





















































































































































1 


MINERS’AND ASS4YERS’ TEXT-BOOK, 


ADAPTED TO THE 

LABORATORY AND SCHOOL. 

PRACTICAL INSTRUCTIONS TO ASSAYER3, 
MINERS AND PROSPECTORS. 

TESTS AND ASSAYS 

OF ALL THE 

PRINCIPAL METAL-BEARLNG ROCKS, 

INCLUDING 



GOLD AND SILVER BULLION. 

I 


-BY- 


y~ 

J. H, FISK, M. E., 

II 

ASSAYER AND ANALYTICAL CHE/VIIST. 


PORTLAND, OREGON: 

THE J. K. G[LL CO., PUBLISHERS. 

1898. 














Tf'iSSc: 


Entered according to Act of Congress in the year 1898 by 

J. H. FISK, 

In the office of the Librarian of Congress 
at Washington, D. C. 


ONF COPY RECEIVED 







ASSAYERS’ AND MINERS’ TEXT BOOK 


ADAPTED TO THE 

LABORATORY AND SCHOOL. 

PRACTICAL INSTRUCTIONS TO ASSAYERS, 
MINERS AND PROSPECTORS. 

TESTS AND ASSAYS 

OF ALL THE 

PRINCIPAL METAL-BEARING ROCKS, 

INCLUDING 

GOLD AND SILVER BULLION. 

-BY- 

J, H. FISK, M. E., 

ASSAYER AND ANALYTICAL CHEMIST. 


I'ORTLAND, OREGON I 

THE J. K. GILL CO., PUBLISHERS. 

1898 . 






The author is well qualified for the work he has under¬ 
taken, the past thirty years having been spent in actual 
practice of his profession; for ten years he was the onfy 
assayer in Portland, during which time he assayed $3,000,- 
000 in gold bullion against the United States Mint without 
an error; he has visited all the great reduction works in this 
country, and thoroughly familiarized himself with all the 
modern methods of treating ores. His principal object 
throughout this work has been, not so much to introduce 
new methods, as to compile, quote and abbreviate from best 
authors, together with his own large experience, and to 
arrange it in such form that the study can be taken up in a 
systematic manner. The book is particularly adapted to 
those who wish to obtain a practical knowledge of assaying, 
having been divested of all extraneous matter and symbols... 
The work has been plainly and carefully prepared and is 
especially fitted for the requirements of the prospector, the 
assayer, and for use in the class room.._ Heretofore much 
difficulty has been experienced by the student, from the 
fact that he has had to Tlig his information out of much 
voluminous reading matter^ which needed many explana¬ 
tions. This book is particularly adapted to colleges and 
universities, the examples and exercises at the end of each 
chapter greatly facilitating the perfect mastery of its con¬ 
tents. It is in three parts," bound in one volume. 

Part First gives particular instructions for the use of that 
delicate instrument, the Assay Balance; and also the Assay 
Furnace; Oxidizing and Reducing Reagents; Solvents and 


Precipitants; An Article on the Assaying of Gold and Silver 
Bullion; The Humid Assay of Silver. 

Part Second describes the Preparation of the Ore Sam¬ 
ple; Weighing of the Charge; Assay of Litharge; Crucible 
Assay; Crucible Assay for Gold and Silver; Melting in a 
Crucible; Scorification; Laboratory Test of Extracting 
Gold by the Cyanide Process; Assay of Tin and Copper 
Ore; Also the Cyanide Process of Assaying Copper Ore; 
Assa}' of Lead; Determination of Iron in an Ore; 
Chromium; Determination of Manganese; Assay of Zinc 
Ores; Of Nickel and Cobalt Ores; Mercury; Assay of Ar¬ 
senic; Assay of Antimony; Assay of Bismuth; Determina¬ 
tion of Sulphur; Assay of Platinum; Coal Analysis. 

Part Three contains Notes of Instruction to those in 
Search of the Precious Metals; Firmness of Rocks; Constit¬ 
uents of Rocks; Metallic Ores Common in Rocks; Ma¬ 
terial of Organic Origin, including a Synopsis of the 
following rare Metals: Barium, Calcium, Chromium, 
Cerium, Lanthanium, Didyniiuni, Columbium, Glueinium, 
Gallium, Indium, Iridium, Lithium Rudidium, Osmium, 
Palladadium, Tantalium, Tellurium, Thorium, Thallium, 
Vanadium, Yettrium, Zicronium, and the ores from which 
they are extracted. Glossary of 125 of the most important 
Minerals; Preliminary Examination of Ores, including 
Diaphaniety, Lustre, Color, Specific Gravity, etc.; Prep¬ 
aration of Pure Gold, Silver, and Lead; Table of Hardness 
and Specific Gravity of 25 Minerals; Blank for Mineral 
Analysis; Tables for the Calculation of Gold and Silver, 


i)oth by Gramme and Grains, also by the Assay Ton; Table 
for Computing Miner’s Inches of Water; Calculation of 
Lead Blast Furnace Charges; Working Test of Gold and 
vSilver Ores ; Extracting Copper by, Chloridizing; Making 
vSilver Amalgam, and much other useful data. 

Price 2.50 Postage Paid. 

Orders for this work will be filled by the publishers or 
author, at Portland, Oregon. 















CONTENTS. 

PREFACE. 

PART 1. 

Page. 

Introduction . 1 

Reference Table . 10 

Implements . 14 

Assay F^irnace . 21 

Assay Balance . 22 

Weights and Weighing . 25 

Reagents . 26 

Solvents . 30 

Precipitants .32 

Reducing Reagents . 36 

Oxidizing Reagents . 36 

Melting Gold and Silver Bullion. 39 

Assaying Bullion . 45 

Assaying Doree and Base Bars. 50 

Humid Assay of Silver Bullion. 54 

Table A for Decimal Salt Solution. 67 

Table B for Decima. Silver Solution. 68 

PART II. 

Introduction to Part II. 73 

Preparation of the Ore Sample. 74 

Weighing the Charge . 79 

Universal Flux . 80 

Mixing the Charge . 80 

Assay of Litharge . 80 

To find the Oxidizing Power of Nitre. 82 

Crucible Assay . 82 

Crucible Assay for Gold and Silver. 86 

1 3 - 
































Page. 

Preliminary Assay . 86 

Dressing the Crucible Assay for Gold and Silver Ores. 87 

Melting in Crucible. 91 

Scorification . 95 

Cupelling ...• 96 

Weighing the Bead . 99 

Parting the Bead .101 

Calculating the Assay .103 

Laboratory Test of Etracting Gold by the. 

Cyanide of Potash Solution .106 

Assay of Tin Ores.109 

Copper Assay .113 

Rich Oxide of Copper Ores..., . 114 

Refining of Copper Button.115 

Cyanide Assay of Copper, wet way.115 

Lead Assay .118 

Determination of Iron in an Ore.123 

Determination by Volume.125 

Determination of Chromium in Ore.129 

DetermJnation of Manganese .131 

Assay of Zinc Ores.135 

Assay of Nickel and Cobalt Ores. 141 

Assay of Mercury.150 

Assay of Arsenic .153 

Assay of Antimony.156 

Assay of Bismuth .158 

Determination of Sulphur .161 

Assay of Platinum .’.166 

Analysis of Coal . 169 

Preparation of Pure Gold and Silver. 173 

To make Pure Lead. 176 


































PART III. 


Page. 

Notes of Instruction to those in search of the precious metals. 181 

Synopsis of some of the rarer and less well-known metals_191 

Preliminary examination of Ores.200 

Glossary of the most important Minerals.207 

Characteristics of Rocks’ Structure. 212 

Firmness of Rocks .212 

Constituents of Rock .212 

Metallic Ores common in Rock.216 

Diaphaneity .218 

Lustre of Rocks .219 

Color of Rocks .221 

Taste of Rocks .222 

Specific Gravity of 25 Minerals.224 

Scale of Color .225 

Blank for Mineral Analysis.226 

To Determine any Mineral.227 

Blowpipe Analysis .229 

Calculation of Lead Blast-furnace Charges.234 

Working Test of Gold or Silver Ores.236 

Aassaying Solutions .238 

Ore in Sight.239 

Extracting Copper by Chloridizing.240 

Estimating percentage of Sulphurets in Quartz.241 

Useful Data .242 

To make Silver Amalgam .242 

Assay Table for 20 Grammes of Ore.245 

Assay Table for A. T. of Ore.246 

Metric or French Weights.247 

C'instruction of A T. with grains.249 

Assay Table for 1 oz. Troy to one-million part of 10 grains. . .260 

Explanation of Assay Ton Weights.252 

Constructing Assay Ton with Grain Weights.253 































Page 2(i. 
Page 3o, 
Page 105. 
Page 105. 
Page 216 
Page 197. 
Page 102. 
Page 216. 
Page 126. 
Page 52. 
Page 253. 


ERRATA. 

Third line from top read Symbol (Na. CO^). 
Exercises No. 21 read Metallic Aluminum. 
Exercises No. 25 read rang, swing and rest. 
Exercises No. 28 read turns black. 

No. 9 read Titanium, not Fitanium. 

No. 1, 2 and 3 read alloys. 

Six lines from top read bumping, not lumbing. 

The symbols should be capitols. 

Third line from bottom of page, read experiment. 
Under Silver value, read 7^4 cents. 

Last paragraph is a repetition. 



PREFACE. 


Among the many valuable works on assaying anl testing 
of the metal-bearing rocks, I am not aware of one, having 
for its special object to explain and render simple to the be¬ 
ginner the various processes employed in assaying and de¬ 
termining the metals quantitatively, which has been devised 
for the illustration of the principles of the science. 

Most of the works I have met with on technical labora¬ 
tory work contain too many methods and much that is 
superfluous which tends to confuse the general student who 
has but a limited time to devote to the subject; while they 
are wanting in those explanatory details, without which he 
must often fail to understand the reason of the operation h« 
is conducting. 

In my long course of some thirty years of varied analyti¬ 
cal practice and teaching, I have often felt the want of a col¬ 
lection of the most improved methods of quantitative deter¬ 
mination of the different metals in an ore, and it is my wish 
to supply this deficiency, and at the same time to furnish a 
text for my own class as well as for the public schools where 
young men and women of the Northwest can obtain a the¬ 
oretical knowledge of one of the greatest industries of the 
country. It is no less valuable to the assayer, the miner and 
the prospector, or to those who have made but little prog¬ 
ress in the science; all will find in it information for their 
guidance. 

My endeavor throughout has been to make everything as 
simple, plain, and practical as possible, and while the meth¬ 
ods I have adopted may not prove superior to some others, 
they are as good as any yet placed before the people. 

In offering this work to the public, I have no expectation 
of its being found faultless; but hope, from the care with 
which the manuscript was prepared, and rigorous compari¬ 
son with the original source, that but few errors have crept 
in, and that the book will prove of value to both school and 
laboratory. 


ABBREVIATIONS. 


B.B. 

Before the Blowpipe. 

S. P. 

Specific Gravity. 

O. F. 

Oxidizing Flame. 

R. F. 

Reducing Flame. 

A. T. 

Assay Ton. 

Gr. 

Grains. 

Gm. 

Grammes. 

H. 

Hardness. 

C. P. 

Chemically Pure. 

P. P. 

Precipitate. 

c. 

Centigrade. 

F. 

Farenheit. 

FI. 

Flame Color. 

On Ch. 

On Charcoal. 


I 


CHAPTER I. 


INTRODUCTION. 

There are many well informed people who suppose that 
the earth consists of one hetrogeneous mass in which sand, 
clay, gravel and a variety of rocks are blended together 
with no more regularity than the ingredients of a plum¬ 
pudding. They suppose that this was its original condition, 
and that the present physical features of the surface, its 
mountains, seas, lakes and valleys, its rocks and its gravel 
existed from the beginning of time as we now see them. 

But no sooner do we begin to penetrate below the surface 
than new views open upon us. There are many districts in 
which it is impossible even to sink a well, or to open a 
quarry or repair a road, without discovering that the rocks 
are arranged in layers and succeed one another in regular 
order. 

All the rocks of the earth’s crust are divided according to 
their structure into classes. The stratified rocks and un¬ 
stratified (or fragmentary). The former are arranged in 
layers. The latter are not. The former are produced by 
the agency of water, the latter by igneous agency or vol¬ 
canic action. The former marks the period of rest in the 
world’s history; the latter chronicles the convulsions upon 
the external crust of the earth. 

Thus looking upon the earth as an organic unit, we may 
study its form, the rocks and minerals of which it is com¬ 
posed, and the manner in which these are arranged; in other 
words, its external form and internal structure, and the sub¬ 
stances of which it is composed. 

All the substances in nature are either simple or com¬ 
pound. A simple substance or body is one from which 
nothing different from itself can be extracted. Charcoal 
and Sulphur are elementary substances. Treat either as you 
may you can extract nothing from them but Charcoal or 


6 


INTRODUCTION 


Sulphur. Chalk and Flint are compound substances. By 
analyzing Chalk we can extract from it a metal called Cal¬ 
cium. By analyzing Flint we can extract from it a sub¬ 
stance called Silicon. Yet sixty years ago no one knew any 
difference, all were supposed to be simple or elementary 
substances. 

There are now about seventy simple substances known, 
and these elements have a tendency to combine one,with 
another,forming compounds; this tendency is called affinity, 
The strength of these affinities differ in different elements, 
one for another under different conditions of temperature, 
pressure, electricity, etc. 

^lost of the elements are known, and all are believed to 
be capable of assuming the solid or gaseous state; some the 
liquid, depending upon temperature and pressure. 

1. These elements may be mixed in any proportion, 
but they can only combine in fixed proportions. When 
elements combine they form a compound wholly different 
in appearance from the elements which composed it. 

2. Two or more solids may combine to form a liquid or 
a gas. Two or more liquids or gases may form a solid etc. 
A knowledge of these compounds and their separation 
forms the basis of Chemistry. 

3. All metals are elements; two or more of them fused 
together form alloys. Hydrogen, Oxygen, Nitrogen, 
Chlorine, Bromine, Iodine, Carbon, Sulphur, Selenium, 
Phosphorus, Boron, Silicon, are simple elements which 
enter into composition of the ores, fluxes, etc., which come 
under the notice of the assayer. But we must remember 
that these elements combine only in fixed proportions. 

4. “The element lead (a metal) combines with the ele¬ 
ment oxygen (a gas) in the proportion of 103.56 parts by 
weight of lead to 8 parts by weight of oxygen, forming 
111.56 parts of litharge. Lead combines with oxygen un- 


INTRODUCTION ^ 

<ier certain conditions in other proportions, but the result¬ 
ing compounds are not litharge.” 

5. The assayer should make himself acquainted with the 
atomic weights of the most common elements. The atomic 
weight of carbon is 12, and of oxygen 16; one part of the 
former combines with two of the latter to form 44 parts of 
the gas called carbon dioxide. If the above is true, the 
same combination would take place if 6 parts of carbon 
were combined with 16 parts of oxygen, making 22 parts of 
carbon dioxide (a gas) or 3 of the former to 8 of the latter. 
Under the action of heat, the affinity of carbon for oxygen 
IS greater than the affinity of lead for oxygen; hence if 
litharge and carbon are heated together, the carbon takes 
oxygen from the litharge and sets the lead free. But this 
action can only take place between definite proportions of 
the substances, as above stated. 

6. If twice 111.56 grains of litharge, containing 16 
grains of oxygen, be heated together with 6 grains of car¬ 
bon, the carbon takes all the oxygen, forming 22 grains of 
carbonic acid gas (carbon dioxide) and the whole of the 
lead is set free; but if more litharge had been present, that 
additional portion would have remained unchanged. 

By this we 'see that 6 grains of carbon reduces 223.12 
grains of litharge, setting free 207.12 grains of lead. Or in 
Other words i grain of carbon produces 34.52 grains of lead 
from litharge. 

7. Other substances take oxygen from litharge under 
heat, in different but fixed proportions for each. Charcoal, 
flour, starch, etc., are impure carbon and each liberates a 
corresponding quantity of litharge. One grain of charcoal 
liberates about 30 grains of lead from a corresponding 
quantity of litharge. One grain of flour will liberate about 
15 grains of lead from litharge. Gum, starch, sugar, etc., 
will each produce their respective amount of lead from 


8 INTRODUCTION 

litharge, in proportion to the amount of carbon they con¬ 
tain. 

8. Nitre (or saltpetre) is composed of nitrogen, oxygen 
and potassium; when heated with lead, it gives off its oxy¬ 
gen which combines with the lead and forms litharge in ac¬ 
cordance with the law of definite proportion. If sulphur or 
carbon be present the oxygen will combine with them be¬ 
cause its affinity is stronger for the two latter than it is for 
the lead. 

9. Compounds can combine with compounds forming 
new compounds. Carbonate of soda or carbonate of pot¬ 
ash when used in assaying are compounds of the metal ele¬ 
ments sodium or potassium with oxygen and carbon diox¬ 
ide. Quartz is a compound of silicon and oxygen. When 
quartz is fused with these alkaline carbonates, the latter is 
decomposed, not into its elements, but into carbonate diox¬ 
ide which escapes with effervescence and the sodium or 
potassium oxide, which combines with the quartz—a com¬ 
pound with a compound—forming glass, (a slag); by this 
means quartz which is not fusible in any common furnace 
heat, is easily converted into a fusible slag. 

10. Again, if you melt a piece of lead in a ladle or dish 
of any kind, you will notice that its surface is at once cov¬ 
ered with a scum; remove it by scraping it off with a stick 
and it will instantly be coated again. Continue doing this 
until all the lead is thus changed into scum or litharge. 
This is merely the lead combining with the oxygen of the 
air and converting it into litharge. Or in other words, it is 
8 parts of oxygen combining with 103.56 parts of lead to 
form litharge. Gold and silver at an ordinary heat do not 
oxidize, but when gold, silver, and lead are melted together 

in the air in a bone-ash cupel, the lead passes off and is ab¬ 
sorbed by the cupel, taking with it all the impurities from 
the gold and silver. This is the philosophy of cupellation. 

11. Again if we place a strip of metallic silver in nitric 


INTRODUCTION 


9 

acid it manifests an affinity for a compound of nitrogen and 
oxygen which exists in the acid; gold does not, hence, when 
an alloy of gold and silver is boiled in nitric acid, the silver 
forms a compound known as nitrate of silver which can be 
crystallized and dissolved in water, but the gold will remain. 

12. In obeying the law of combination in definite pro¬ 
portion it is necessary that we have acid present in suf¬ 
ficient quantity, otherwise a part of the silver will remain 
unaltered; if more acid than the required amount be used, 
the excess of acid will remain unchanged. 

In practice, it is necessary in assaying bullion that the 
alloy contain at least twice as much silver as gold, other¬ 
wise the insoluble gold will so envelop the silver as to pro¬ 
tect it from the action of the acid, leaving some silver in the 
gold, which would render the assay incorrect. 

The art of assaying is dependent on the laws of chemistry, 
and may be practiced with considerable success, but can 
never be properly understood unless these laws are studied. 

The table on the next page contains the names of thirty- 
six elements, because they are more frequently used than 
the others, and the only ones treated of in this book. 


10 


INTRODUCTION 


REFERENCE TABLE. 


Symbol. 

Quality. 

j Atomic 

1 Weight. 

Strength. 

O 

Negative end. 
Oxygen 

16 

2 

s 

Sulphur 

32 

2 

N 

Nitrogen 

14 

3 

F 

Fluorine 

19 

1 

Cl 

Chlorine 

35.5 

1 

Br 

Bromine 

80 

1 

I 

Iodine 

127 

1 

CN 

Cyanogen* 

26 

1 

Se 

Selenium 

79 

2 

P 

Phosphorus 

31 

&-(3) 

As 

Arsenicum 

75 

3-(5) 

Cr 

C romium 

52.5 

2 

B 

Boron 

11 

3 

C 

Carbon 

12 

4-(2) 

Sb 

Antimony 

122 

3-(5) 

SI 

Silicon 

28 

4 

H 

HYDROGEN 

1 

1 

Au 

Gold 

19G.6 

3-(l) 

Pt 

Platinum 

197 

4-(2) 

Hg 

Mercury 

200 

2 (Hg «2 a dyad> 

Ag 

Silver 

108 

1 

Cu 

Copper 

63.5 

2 (Cu 2 a dyad) 

Bi 

Bismuth 

210 

3 

Sn 

Tin 

118 

4-(2) 

Pb 

Lead 

207 

2-(4) 

Co 

Cobalt 

59 

2 

NI 

Nickel 

59 

2 

Fe 

Iron 

56 

2 (Fes a hexad) 

Zn 

Zinc 

65 

2 

Mn 

Manganese 

55 

2—(4) 

A1 

Aluminum 

27.5 

AI 2 a hexad. 

Mg 

Magnesium 

24 

2 

Ca 

Calcium 

40 

2 

Sr 

Strontium 

87.5 

2 

Ba 

Barium 

137 

2 

Na 

Sodium 

23 

1 

K 

Potassium 

39 

1 

H N 

Ammonium* 

18 

1 


Positive end. 




* Not elements. 





















INTRODUCTION 


II 


For a further illustration on the art of assaying I cannot 
<io better than quote from Aaron in his valuable little work; 
part first on gold and silver assaying: 

“An assay is an operation performed on a known quan¬ 
tity of matter for the purpose of ascertaining how much of a 
certain substance that quantity of that kind of matter con¬ 
tains. A test is an operation performed on an indefinite 
quantity of matter in order to ascertain the character of that 
matter, or to determine the presence or absence of some 
particular substance. Thus, to test a piece of rock for sil¬ 
ver is merely to try whether it contains any silver or not; to 
assay it for silver is to find out how much silver is contained 
in a weighed quantity, as an ounce or a half ounce, and 
thence, by calculation, in a ton of such rock. Testing may 
often precede assaying with great advantage because it en¬ 
ables us to know what kind of matter we have to deal with, 
and thus to adapt our method so as to insure a correct as¬ 
say; or it may show us that an assay would be useless be¬ 
cause of the adsence of the substance sought, or of its pres¬ 
ence in such minute quantity only as to be practically 
worthless. 

“To avoid confusion hereafter it is as well to mention that 
not only the act of assaying but also the definite quantity of 
matter operated on, is called an assay. Also, a test is either 
the act of testing, the thing tested, or the agent by means of 
which a test is made. 

“Assays and tests are of two principal classes, the dry, or 
fire, and the wet, or humid assay or test. In the dry way the 
substance under examination is usually melted by heat, with 
the addition of such substances as may be necessary to pro¬ 
duce fluidity and to separate the particular substance sought 
from the other components. The added substances are 
called fluxes, reducers, oxidizers, desulphurizers, etc., ac¬ 
cording to their functions in the operation. In the wet 


12 


INTRODUCTION 


way the substance, if solid, is acted on by means of liquid 
solvents such as acids, etc., which convert it, wholly or in 
part, into a liquid. By the addition of ‘"reagents” to the 
liquid, the substance sought is separated, or its presence and 
in assays its quantity is determined by the occurrence of 
some appreciable phenomenon such as the production of a 
precipitate or of a color. For example, a portion of pure 
bullion is dissolved in nitric acid and a solution of common 
salt is added; the formation of a white precipitate indicates 
the presence of silver; this is a test. If the portion of bul¬ 
lion be weighed, and the exact quantity of salt required for 
the complete precipitation of the silver be also ascertained, 
the proportion of silver in the bullion is easily deduced; 
this is an assay. Again, a substance supposed to contain 
copper is dissolved in acid, and ammonia is added; the pro¬ 
duction of a blue color indicates that copper is present, and 
if the portion of the substance be weighed before being dis¬ 
solved we can ascertain how much copper it contains by 
noting how much cyanide of potassium it takes to destroy 
the color. 

“Silver ores are assayed in the dry way, gold ores by a 
combination of the dry and the wet way. By ores is here 
meant all mineral rock, or earth, containing the metal 
sought in small particles, or in chemical combination. Sil¬ 
ver ores very frequently contain gold, and gold rarely oc¬ 
curs quite free from silver. The ore is ground to a powder, 
weighed, and melted in an earthen vessel (crucible or scori- 
fier) with fluxes including lead in some form; a glassy mass 
(slag) and a lump of lead (button) result. The lead con¬ 
tains the precious metal, and is melted on a porous support 
(cupel) in an oven (muffle), converted into litharge and ab¬ 
sorbed by the support. The gold and silver remain in the 
form of a bead on the support; the two are parted by boiling 
the bead in nitric acid.” 


INTRODUCTION 

EXERCISES. 


13 


1. What is the difference between mixing and combin¬ 
ing? 

2. In how many forms do the elements appear? 

3. When two or more metals are fused together what 
is the result called? 

4. In what proportion do lead and oxygen combine? 

5. What are the combining weights of lead and oxygen? 

6. By fusing 6 grains of carbon with litharge, how 
much lead is set free? 

7. Name four substances that will reduce litharge to 
metallic lead. 

8. When nitre is melted with lead, what is the effect? 

9. What is the result when carbonate of soda and 
quartz are fused together? 

10. What is the philosophy of converting lead into 
litharge? 

11. What is the effect of boiling a strip of silver in nitric 
acid? 

12. Explain the law of definite proportion. 

The teacher should fully illustrate and explain each ques¬ 
tion. 


14 


IMPLEMENTS 
CHAPTER II. 


IMPLEMENTS. 

It is of little use to describe and illustrate the different 
implements used in assaying, such as the various kinds of 
pulverizers, grinders, mortars, scales, muffles, furnaces, 
tongs, molds, scorifiers, crucibles, funnels, glassware, mat- 
trasses, etc. How to use them can never be learned from 
books; nothing but the actual handling of them under the 
direction of a competent instructor will enable one to avoid 
their wholesale breakage and destruction. All these arti¬ 
cles can be purchased of John Taylor & Co., 63 First street, 
San Francisco. To set a student to work without instruc¬ 
tion in their manipulation would cost more in breakage 
than his tuition. There is a right and a wrong way to 
handle the implements in an assay office as well as in other 
professions. One ounce of practice is worth a pound of 
theory. 

In addition to the foregoing the apparatus necessary for 
a well regulated assay office is extensive and expensive, and 
much of it has to be made up as the work calls for it, al¬ 
though it is necessary to keep quite a stock on hand of 
crucibles, scorifiers, cupels, casseroles, beakers, and funnels 
and an assortment of filtering paper, as well as pipettes and 
burettes, and flasks, together with the common stock of 
chemicals necessary for all kinds of work. 

The following are indispensible; Shovels, pokers, scrap¬ 
ers, crucible tongs, scorifier tongs, cupeling tongs, cold- 
chisels and small anvil, spatulas, steel dies from o to 9 for 
marking bullion bars, cutting shears and nippers, an assort¬ 
ment of glass and rubber tubing, platinum wire and foil. 
Most of the apparatus used can be purchased of the dealers 
but with a little patience and practice a great deal of it can 


IMPLEMENTS 15 

be made in the laboratory. In purchasing apparatus and 
supplies, it is always cheaper in the end to buy the best. 

It is not necessary that the student should memorize 
formulas, atomic weights, strength, etc. Let the pupil per¬ 
form all the experiments he has a mind to, but not under¬ 
take the most difficult ones without assistance. This meth¬ 
od takes time, but it is the only way to teach the use of the 
small flasks, test tubes, and small quantities of chemicals. 
Do not be afraid to teach anything contrary to the text if 
you have good authority for it, and let disputed points 
alone; teach any simple principal outside the text instead 
of more complex matter. Use the metric system. Use 
either thermometer. Centigrade (C) or Farenheit (F). 

The following illustration will show an easy and con¬ 
venient way and the other an awkward and clumsy way of 
doing work in simply pouring an assay into a mold. 


i6 


IMPLEMENTS 



THE NEW BEGINNER 











IMPLEMENTS 


17 







ONE WHO HAS LEARNED 






i8 


lAIPLEMENTS 


The above is a fair illustration of a thousand and one 
manipulations conducted in assaying and which can never 
be learned from books. While the student may read and 
study everything ever written on the subject, unless he has 
practical instructions in the handling and the use of the 
instruments, he will find himself conducting a very expen¬ 
sive business; for example: A few drops of cold water cn 
a hot dish would cost him several dollars, besides ruining 
the results of his assay; a sudden heating or cooling of 
glassware in use would produce the same results. Or, the 
smallest particle of lead brought in contact with a platinum 
dish under heat would entail an expense of $5 to $10 in re¬ 
pairing the damage. 

It is very important that the student should at once begin 
to make careful notes of all the experiments he engages in. 
He should endeavor to do this in as concise and methodical 
a manner as possible and he will find it very advantageous 
to make use of symbols in describing the substances he em¬ 
ploys, and the changes whicr they undergo; he will thus be 
able to record much in a small space, and at the same time 
he will be making himself familiar with the composition of 
the substances with which he is experimenting. 

The student will soon learn by experience that he cannot 
be too methodical in his operations, or too careful in culti¬ 
vating habits of neatness and cleanliness. 

It is not enough that the student should be able physical¬ 
ly or mechanically to make up an assay charge of free-mill¬ 
ing ore and assay it correctly; but he should know the re¬ 
action of each flux added and the function it performs. The 
public is already abundantly supplied with quack assayers, 
as well as quacks in other professions (and it is with more 
feelings of pity than censure that we admit it.) Such an 
one is he who would make an incorrect return for the pur¬ 
pose of pleasing his patron and encouraging him to spend 


IMPLEMENTS 


19 


much time, labor, and money, in further development of his 
mine, only to find out at last that he has nothing; and a 
quack assayer of this kind deserves the severest censure. 

I have often noticed that the newly-fledged assayer, who 
has merely learned how to assay a free-milling ore, is very 
proud of his achievement, priding himself on his superior 
knowledge, but he should not forget that there is always 
room for improvement, and not be so ready to condemn 
others who do not work in the same manner. 

It would look better for such assayers to say less, and 
study more, for they might be called upon to check up with 
older and better-regulated establishments, on rebellious 
ores, when they would find themselves deficient in many 
things. 

The art of assaying any and all kinds of ores is not so 
easy as many are led to believe. 

Every one who has been engaged in assaying and analyt¬ 
ical work knows that cases will sometimes occur, especially 
in commencing the study, in which doubts may be enter¬ 
tained as to whether the results will turn out correctly. For 
instance, a small portion of the substance under investiga¬ 
tion may be spilled, or the assayer may have doubts of the 
accuracy of his weighing; or he may not have sampled his 
ore correctly, or used the proper dressing for his assay 
charge; or got his numbers changed; or the charge in his 
crucible may boil over, causing a loss—all these things and 
a hundred more I might add are as much a part of the edu¬ 
cation of the assayer as the determination of the results. 

In all such cases it is indispensable that the operator 
should throw away his blemished work and be conscienti¬ 
ous enough to repeat the whole process over. He who is 
not possessed of this self-command; who shirks trou¬ 
ble where truth is at stake, who would be satisfied with 
mere guess-work where the attainment of positive certainty 


20 


IMPLEMENTS 


is the object, must be pronounced a fraud. He, therefore, 
who cannot trust his work and cannot swear to the correct¬ 
ness of its results, had better occupy himself in some other 
avocation. 

There are two very indispensable articles in assaying 
that need more than a passing notice; these are the 
assay furnace and the balances. In my varied practice I 
have used all kinds of assay furnaces, large and small. For 
small, ordinary work I have constructed a combination fur¬ 
nace which, for convenience and durability, I find excels 
all other coke and coal furnaces I have met with, and which 
I believe has been adopted by most of the assayers of the 
Northwest. It is portable with a hood which fits snugly 
down over the top and with a working door in the hood 
which carries off all the dirt and smoke. Its form is square 
and it need not be over i8 inches high, and nine and one- 
half inches square, inside measurement. It also has loose 
grate bars which greatly facilitate the cleaning process. 
Four assays can be melted at one time in it. For melting 
much gold dust in a plumbago crucible it is better to have 
the furnace 20 inches high. The Ploskins gasoline furnace 
is a very convenient and cleanly method of melting ores, as 
the gasoline can be had cheaply, and is quite a saving on 
muffles. 


IMPLE^ilEXTS 


21 















22 


IMPLEMENTS 



Assay Balance 












THE ASSAY BALANCE 
CHAPTER HI. 


23 


THE ASSAY BALANCE. 

No reliable assayer will use a cheap grade balance, for 
while many of them may do for prospecting, etc., where re¬ 
liable work is to be done for the public none but the very 
best should be used. The Ortling, No. 12, $175; No. 12 A, 
$225; No. 12 B, $175; and his best No. 12 C, $250, are all 
reliable and good balances. Beckers’ No. 4, $135, is a fair 
balance. Troemners’ No. 5, $175, is also a good balance. 

I am told that the Ainsworth balance, manufactured in 
Denver, is a very fine one. There are many grades of 
prices and qualities of balances down to Troemners’No. 3 at 
$40; but after a little use I have found them wholly unrelia¬ 
ble, for to the assayer the assay balance is the most im¬ 
portant instrument of his whole outfit, being really what 
determines his results, and great care should be taken for 
their preservation and adjustment. The general public, 
however, knows very little about this instrument; nine out 
of ten would as implicitly trust their work to one of these 
cheap instruments as they would to the very best, although 
the results below $10 per ton are mere guesswork. A good 
balance should have a double sliding rod called a carrier, 
and should be furnished at its inner end with an arm ex¬ 
tending at a right angle to the rod over the beam. On 
these arms hang the riders, each of known weight, so that 
when placed on the beam equal distances from the center, 
they will equally balance if otherwise properly adjusted. 

By means of these carriers, operated from without the 
case, either of the riders can be placed upon the beam at any 
point desired, or removed at pleasure. The rider acts upon 
the principle of the pea on a steelyard, and is used to com¬ 
plete the weighing of an object on the balance without 
opening the case. The balance must be placed on a solid 


24 


THE ASSAY BALANCE 


table, or a shelf fastened to the wall of the building where 
no jarring of the premises can be felt. An open dish of 
quicklime should be kept in the balance case to absorb the 
moisture from the atmosphere. 

1 he weights used with this balance are either grains or 
grammes corresponding with those used in weighing the 
ore for the assay. If in grains the set is from ten grains to 
one one-hundredth grain, or one one-thousandth of the ten 
grains. If in grammes, from one gramme to one milli¬ 
gramme. In either case the smaller is one one-thousandth 
part of the larger, and the system is the unit of one. The 
rider is used for smaller weighing of the fractions of these 
units, and must agree with the other weights of the set used, 
and with the number of divisions on the beam. In most 
cases the beam has five principal divisions on each arm and 
fifty subdivisions. 

I doubt if any instruction can be properly given to a 

student for the adjustment of an assay balance without the 

p;actical illustration wdth the instrument itself, any more 

than can the repair or adjustment of a watch. Occasionally 

the balance may be dismounted and the parts cleaned with 

a soft chamois leather, and all dust removed from the beam 

\ 

with a camels’ hair brush. One weight of the set should 
cause the index or pointer to swing one-tenth division from 
zero, and one-tenth obtained by the rider should cause a 
deviation of one division. The deviation should be the 
same on either side with the same excess of weight; if oth¬ 
erwise, the balance is a bad one. 

I have known some assayers to make daily returns for 

years with an old and cheap balance full of dust and dirt, 
and which should never have been used at all. I may say 

here that no careful assayer would use such a balance, or 
his weights without testing them. 


THE ASSAY BALANCE 
WEIGHTS AND WEIGHING. 


25 


I have had some difficulty in getting students to correctly 
set down their weights when weighing; they will frequently 
get the units and tenths of units mixed, placing the units 
where the hundredths should be, and the tenths of units 
where the units should be, and vice versa To make it plain 
it is only necessary to remember that we are dealing with 
one thousand. For instance, in $10 there are 1000 cents, 
and in setting down our weights it is only necessary to 
place our dollars where our dollars should be, and the cents 
where the cents should be, and the mills where the mills 
should be, in the parts per thousand, and these are our as¬ 
say weights. 

The weighing of a bead or piece of precious metal ob¬ 
tained by an assay is “reported” in units of the set, not in 
grains or grammes. Thus, a bead weighing 1.145 grains is 
reported as 114.5; one weighing 0.0445 grammes is reported 
44.5. One gramme or ten grains is therefore called 1000. 
An assay is simply a question of the proportionate weight 
of precious metal as compared with the weight of the ore 
from which it was extracted; and the weights used in 
weighing the ore for the assay must accord with those used 
in weighing the metal obtained. The proportion once as¬ 
certained, it is easy to deduce ihe absolute quantity of metal 
in a ton. 

The 1000 assay weights should equal the 400, 300, 200, 
and 100 assay weights together; the 400 should equal the 
300 and 100; and so on down the whole set of weights. It 
is not important that the weights should absolutely be stan¬ 
dard, but they should be correctly proportioned one to the 
other. 


26 REGENTS 

■ CHAPTER IV. 

REAGENTS. 

1. The following are the principal fluxes used in dry or 
fire assays: 

Sodium bicarbonate (NaHCOg)—carbonate of potas¬ 
sium will answer the same purpose—acts as a desul¬ 
phurizing agent or basic flux, and in some cases as oxidiz¬ 
ing agent. It should be free from moisture and dried in a 
clean pan before using. It fluxes quartz rock, desulphur¬ 
izes galena and some other sulphurets. Mix some pow¬ 
dered (juartz with thrice its weight of soda, heat to a bright 
redness in a crucible: the result will be glass when poured 
out. 

2. Borax, 2NaB02, B2O;., 10H2O. To prepare for use. 
—Heat it gently in an iron pan until it swells no more, then 
cool and grind it; it should not be melted, as that makes it 
hard to grind. Borax may be bought already ground, and 
may be used in this way without drying. It fluxes clay, 
lime, magnesia, slate, etc., and metal oxides generally; also 
quartz, but not so well as soda. Borax glass is made by 
melting in a clean crucible cast in thin plates on a flat iron, 
then grinding to powder; one part by weight is equal to two 
of undried borax, and does not swell. 

3. Litharge (PbO)—Lead Oxide. It fluxes most rocks, 
earths, and metal oxides, and is very destructive to cruci¬ 
bles if used in excess, for which reason other substances, to 
a certain extent, are used in place of it. It is an oxidizer 
because it gives up its oxygen to combustible substances, 
causing them to burn or become oxidized; it thus burns 
sulphurets in an assay, and although all the substances are 
not burnt out, their conditions are changed and converted 

into their respective products of combustion. It is a de- 
sulphurizer because it burns the sulphur of sulphurets, as 
well as oxidizing its metals, except lead and the noble 


REGENTS 


27 

metals; is a source of lead in the assay by giving up its oxy¬ 
gen, leaving the lead in a metallic state. 

4. Glass, (S2O2) common bottle or windo'w—Acts like 
borax but harder to melt. Used in an assay when it con¬ 
tains much lime or clay but not with quartz. Useful in an 
assay when much nitre or litharge is used. It is an acid 
flux. 

5. Lead Flux.—A mixture of 16 parts of bicarbonate of 
soda and 16 parts of carbonate of potash, 4 parts of flour, 
and 8 parts of borax glass is an old lead flux and a good 
one, because it is both a reducing and a desulphurizing 
agent. 

6. Black Flux consists of one part of nitre and three 
parts of argol (deflagrated). This is an old flux recom¬ 
mended by Mitchell, but it is not much used now, and with 
all the other modern fluxes it is superfluous. 

7. Nitre or Saltpetre (KNO3) is a powerful oxidizer, then 
a flux and a desulphurizer. When fused gives oflf large 
quantities of oxygen, leaving the potash as a flux the same 
as soda. Nitre oxidizes all metals except gold and pla¬ 
tinum; used to counteract the effect of too great a quantity 
of sulphurets in an assay, which it does by burnig a part of 
them which would otherwise produce too much lead from 
the litharge. To determine the oxidizing power make up 
the following charge, place it in a clay crucible and fuse in a 
hot fire. Remove, pour, cool, and weigh the lead button. 
The difference between the weight of the lead button ob¬ 
tained and that given in the determination of the reducing 
power of charcoal divided by 1.5 gives the oxidizing power 
of nitre per gramme: 

Charge—Litharge.30 grammes. 

Soda Bicarb. ... 15 grammes. 

Charcoal . 0.5 grammes. 

Nitre. 1.5 grammes. 





28 


REGENTS 


8. Sulphur—Used in a certain class of assays in cer¬ 
tain cases to prevent copper from entering the lead button, 
which it does by converting the copper into a sulphuret; 
but no instructions can be given as to what kind of copper 
ores it should be used in. It must be left to the intelligence 
of the assayer alone. 

9. Iron (Nails) is a good desiilphurizer for galena and 
for compounds of silver with sulphur, but not for copper or 
zinc ores. It can take all the sulphur and arsenic from lead 
and silver ores, setting these metals free; but it can only 
take a part of the sulphur from iron and copper pyrites and 
some other sulphurets, leaving a part of the metals com¬ 
bined in the form of matte. 

10. Potassium Cyanif'.e (K C N) is a powerful reducing 
and desulphurizing agent. It is used for the determinatiou 
of tin, bismuth, and sometimes antimony by fire assays, and 
for the wet assays of copper. It should be pure and free 
from sulphides and sulphates. 

11. Argol (K H C4 H4 Oc). Commercial bitartate of 
potash. This is also a powerful reducing agent and a basic 
flux. Its reducing power should be determined by fusing 
with litharge and carbonate of soda. 

12. Charcoal (C) acts as a reducing agent and a desulphur- 
izer like flour, starch, sugar, etc., but their reducing power 
must be determined before using to know the amount of 
carbon they contain. 

II. Salt (Na Cl) is used principally as a cover in cruci¬ 
ble assays. Glass of borax is equally as good, washing the 
sides of the crucible. If mixed with the assay it tends to 
prevent overflowing by becoming fluid at a low temperature 
and facilitating the escape of gases. 

14. Granulated Lead (Pb) acts as a basic flux and col¬ 
lector of the precious metals. Used in scorification assays 
in which the litharge required as a flux is produced from 
lead. 


REGENTS 29 

15. Sheet Lead must contain no gold or silver. Used 
in bullion assays for cupelling off the base metals. 

All the above fluxes should be dry and pulverized and 
kept in their respective boxes with covers where they will 
not become contaminated. 

EXERCISE. 

1. What are the two principal fluxes used in fire assays? 

2. For what is borax used in the fire assay? 

3. For what is litharge used and what function does it 
perform? 

4. What is the use of glass? In what kind of ores? 

5. What is a good flux for a lead ore assay? 

6. What is black flux? 

7. State the use of nitre in an assay. 

8. For what purpose, and in what class of ore assays is 
sulphur used? 

9. What is the use of iron nails? In what kind of ores? 

10. In what kind of ores is potassium cyanide used? Is 

it a reducer or desulphurizer or both? 

11. What is argol? For what purpose is it used? 

12. State the use of charcoal. What is the difference 
between charcoal and argol? 

13. Mention the use of salt. 

14. In what kind of ore assays is granulated lead used? 

15. In what kind of assays is sheet lead used? 


SOLVENTS 
CHAPTER V. 
SOLVENTS. 




The following are the principal fluxes used in wet assays 
or chemical analyses and as solvents during fusion. 

1. Carbonate of soda (N02 CO3) acts as a decomposing 
agent and is used for the decomposition by fusion, either 
alone or in conjuction with other reagents such as carbon¬ 
ate of potassium (Kg CO3) or nitrate of potash (K N O3), 
A mixture of the two carbonates in porportion to their 
molecular weights is a most excellent flux for the decom¬ 
position of certain silicates, clays, etc., which are with dif¬ 
ficulty decomposed by either carbonate alone. They 
should be pure and free from moisture. 

2. Potassium bisulphate (K H S OJ. This is a decom¬ 
posing agent as well as an acid flux. Silica is not rendered 
soluble by fusion with it, while iron oxides, alumina, etc., 
are converted into a form which is soluble. 

3. Sodium hydrate (Na O H) acts both as a decompos¬ 
ing agent and a basic flux. It is used principally for the 
decomposition of sulphides and sulphates in the determina¬ 
tion of sulphur. It is sometimes used for the decomposi¬ 
tion of certain silicates. 

4. Potassium hydrate (K O H) acts the same as sodium 
hydrate and is used for the same purpose. 

5. Hydrofluoric acid (H El) is one of the most powerful 
decomposing agents. P>y it most of the silicates are decom¬ 
posed and volatilized : it is kept in gutta percha bottles and 
must never be allowed to touch the hands as it makes a 
very bad sore. 

6. Water (HgO). Used in analyses for solution, dilu¬ 
tion, etc. Should be pure distilled. Snow or ice water will 
do if filtered and clean. 

7. Hydrochloric acid (H Cl). This acts as a powerful 
solvent, either alone or in conjunction with other acids.. 


SOLVENTS 


31 

Three parts of hydrochloric acid and one of notric acid form 
aqua regia, one of the most powerful solvents. It dissolves 
gold and platinum. Should be pure. 

8. Nitric acid (H N Oo) is a powerful solvent and oxi¬ 
dizing agent. It should be pure and kept on hand in con¬ 
centrated and dilute state. The specific gravity should be 
1.2. 

9. Sulphuric acid (H^, S 0_t) is a great solvent and is 
extensively used both as a solvent and a precipitant. The 
specific gravity of the concentrated acid is 1.84. The dilute 

is prepared by adding one part by volume to five volumes 
of water. 

10. Acetic (HC2 H3 0^)1 Oxalic (H^. O4), Citric 

(Hg C,j H5 O7, Ho O) and tartaric acids H., Og) are 

all weak solvents and are much used for special purposes. 

Acetic acid comes in solution C. P. The other acids come 
in crystalline form. 

AH these acids are best used in a chemically pure state— 
are marked C. P. In making up these solutions it is best 
to use an excess of the reagents, thus making a saturated 
solution. 

11. Ammonium acetate (NH^ Co Hg Oo) is a great 
solvent for lead salts, especially lead sulphate. The best 
method of making it is by adding strong acetic acid to 
strong ammonia water until the solution is just acid, and 
th en adding a few drops of ammonia to render the solution 
alkaline. 

12. Ammonia (NH^ O H) acts as a powerful solvent of 
the chlorides and bromides of silver. 

13. Sodium hyposulphite (Nag H2 S2 • OJ is a solvent 
of silver chlorite and is largely used in leaching of silver 
ores. 

14. Potassium cyanide (K C N) is a solvent of gold and 
silver and is extensively used in extracting the gold from 
the ore. 


32 SOLVENTS 

15. Ammonium sulphide [ (N H 4) 2 S] is a powerful 
solvent of the sulphides of arsenic, antimony and tin. 

EXERCISE ON SOLVENTS. 

1. How is oxygen made, and for what is it used? 

2. State the difference between potassium bisulphate 
and carbonate of soda as solvents. 

3. What are the three uses of sodium hydrate? 

4. What is the principal use of permanganate of potash? 

5. How, and for what is hydrofluoric acid used? 

7. Eor what is hydrochloric acid used? What is aqua 
regia? 

8. Is nitric acid an oxidizer or a reducer? 

9. Eor what is sulphuric acid used as a solvent, and what 
does it precipitate? 

10. What is the use of acetic acid? 

11. What is the use of ammonia acetate? 

12. What are the uses of ammonia? 

13. What is sodium hyphosulphite a solvent for? 

14. What is potassium cyanide a solvent for? 

15. What is ammonium sulphide a solvent for? 

^ t 

PRECIPITANTS. 

There are a large number of precipitants used in wet as¬ 
says of which only a few will be mentioned here. 

1. Barium chloride (Ba CI2). Used as a precipitant for 
sulphuric acid. In making up the solution one gramme of 
the salt is added to 10 c.c. of water. One c.c. of this 
solution wfll precipitate 0.0327 grammes of S O3. 

2. Hydrodisodic phosphate (Nag HPO4). This is 
used principally to precipitate magnesia from ammonia so¬ 
lution. In making up the solution one gramme of the 
crystalline salt is added to 10 c.c. of water. One c.c. of 
this solution will precipitate 0.012 grammes of Mg. O. 

3. Ammonium oxalate [ (N H4) C2O4] is used prin- 


PRECIPITANTS 


33 

cipally as a precipitant for calcium. In making up the so¬ 
lution one gramme of the salt is added to lo c.c. of water. 
One c.c. of this solution will precipitate 0.0145 grammes 
Ca O. 

4. Magnesia mixture is used as a precipitant for phos¬ 
phorus and arsenic. To make the solution take i gramme 
of Mg C O4 (salt), I gramme of N Cl (salt), and 4 c.c. 
of ammonia and add to 8 c.c. of water. One c.c. of this 
solution will precipitate 0.024 grammes of P2O5. 

5. Molybdate solution is also used as a precipitant for 
phosphorus and arsenic. In making up the solution I 
gramme Mo O3 is dissolved in 4 c.c. of ammonia and the 
solution is poured into 15 c.c. of H N O3 —S. P. 1.2. 
One c.c. ot this solution will precipitate 0.0013 grammes 
of P2 Og. 

6. Silver nitrate (Ag N O3) is used principally as a pre¬ 
cipitant for chlorine. To make up the solution i gramme 
of salt is added to 20 c.c. of water. One c.c. of this solu¬ 
tion will precipitate 0.0104 grammes of Cl. 

7. Potassium chlorate (K Cl O3) is a great oxidizer used 
precipitant of Mn O2, also in volumetric estimation of iron. 

8. Ammonia (NH^ OH) is used as a precipitant of iron, 
alumina, and is much used in laboratory work. 

9. Ammonium carbonate [ (N H^) 2C O3] is used to 
precipitate Zn, Mn, FI, Ca, Ba, etc. To make the solution 
take I gramme of the salt and i c.c. of ammonia and add 
to 4 c.c. of water. 

10. Ammonium sulphide [ (N H4) 2S] is used as a pre¬ 
cipitant of Fe, Z, Mn, Ni, and Co. To prepare the solution 
pass a strong current of pure sulphuretted hydrogen 
through two parts of ammonia, then add three parts of 
ammonia to it. Keep well corked and in a dark, cool place, 
as it loses strength. 


34 PRECIPITANTS 

11. Ammonium chloride (N Cl) is used with am¬ 
monia to precipitate iron. 

12. Sodium carbonate (Na2 C03) is used to precipitate 
Zn, Fe, Mn, Ca, Ba, etc. A saturated solution is best for 

use. 

13. Sodium sulphide (Na2 S) is used as a precipitant for 
the heavy metals and is a solvent for the sulphides of arsenic, 
antimony and tin. To prepare it add i gramme of the salt 
to 10 c.c. of water. 

14. Sodium acetate (Na C2 H3 O2) is used to precipi¬ 
tate iron and alumina in the basic-acetate separation of these 
metals. 

15. Sodium chloride (Na Cl) is used to precipitate silver 
both in gravimetrical and volumetric determination. 

16. Platinic chloride (Pt CI4) is used to precipitate po¬ 
tassium. To prepare it dissolve i gramme of the metal in 
aqua regia; evaporate to dryness, and dissolve in one c.c. 
H Cl and 9 c.c. of water. One gramme of this solution 
will precipitate 0.048 grammes of K2 O. 

17. Hydric sulphide or sulphuretted hydrogen’ (H2 S). 

Used to precipitate all heavy metals. To prepare the gas 
add dilute sulphuric acid to iron sulphide, and wash the gas 
by passing it through the water. 

18. Sulphuric acid (H2 SOJ is used to precipitate bar¬ 
ium, lead,^tc. One gramme of the dilute acid will precipH 
itate 0.4291 grammes of Ba. 

19. Metallic zinc (Zn) is used to precipitate Pb, Cu, As, 
Sb, Ag, and Au from cyanide solution. The zinc is used in 
the form of sheets or granulated zinc, but for precipitating 
gold from cyanide solution it should be in the form of zinc 
shavings, thus preventing a deposit on the zinc plates by 
forming a hydrogen film on the zinc. 

20. Metallic copper (Cu) is used to precipitate mercury. 
Should be used in the form of thin foil and sheets. 


PRECIPITANTS 


35 

21. Metallic aluminum (Al) is used to precipitate copper 
and bismuth. Should be used in the form of sheets or foil. 

Pure material should always be used. In making up the 
solution the water must always be pure. 

EXERCISES ON PRECIPITANTS. 

1. For what is Ba Cl used as a precipitant? 

2. How would you make up a solution of hydrodisodic 
phosphate? 

3. For what is ammonium oxalate used as precipitant? 

4. How is magnesia mixture made? 

5. In what way is molybdate solution used? 

6. How many grammes of chlorine will a c. c. of silver 
nitrate precipitate? 

7. What is the use of potassium permanganate? 

8. What is the use of ammonia? 

9. How would you make a solution of ammonium car¬ 
bonate? 

10. How would you make a solution of ammonium stll- 
phite? 

11. For what is ammonium chloride used? 

12. What will sodium carbonate precipitate? 

13. What will dissolve arsenic, antimony, and tin? 

14. What is the use of sodium acetate? 

15. When is sodium chloride used? 

16. How would you prepare a solution of platinic 
chloride? 

17. For what is hydric sulphide used? 

18. How much Ba will one gm. of dhute sulphuric acid 
precipitate? 

19. In what form is metallic zinc used? 

20. What will precipitate mercury? 

21. What will metallic chromium precipitate? 


36 REDUCING REAGENTS 

CHAPTER VI. 

REDUCING REAGENTS. 

All of the following class of reagents have the power of 
removing oxygen from its compounds. They are the re¬ 
verse of oxidizing reagents. 

The principal reducing reagents used in the fire assays 
are argal, charcoal, flour, starch, sugar, potassium, ferro- 
cyanide, and potassium cyanide already mentioned under 
the head of “Fluxes.” 

The following are the most important of the reducing re¬ 
agents used in the wet analyses: 

1. Hydrogen (H) is a most powerful reducing agent 
used in the form of gas the same as sulphuretted hydrogen. 
It is best prepared by treating zinc with dilute sulphuric 
acid. 

2. Sulphuretted hydrogen (HoS) is also a powerful re¬ 
ducing agent. The gas is prepared in the manner described 
under the head of precipetant. 

3. Sodium sulphite (Na^ SO.J. This is a good reduc¬ 
ing agent. Used for the reduction of ferric solutions. It 
separates arsenious sulphide, which is soluble in it, from 
the sulphides of antimony and tin which are insoluble in it. 

4. Stannous chrolide (Sn CL) is used for the reduction 
of iron solutions for the volumetric estimation of iron. It 
is also used for the detection of gold in solution by forming 
a purple color. 

There are many other organic compounds, such as tar¬ 
taric acid, sugar, etc., which will serve as reducing agents. 

OXIDIZING REAGENTS. 

The oxidizing reagents most often used in fire assaying 
are nitre, litharge, sodium bicarbonate, and oxide of iron. 

The following are the principal oxidizing reagents used 
in wet analyses: 


OXIDIZING REAGENTS 


37 

1. Oxygen (O) is a most powerful oxidizing agent, and 
is produced by using chlorate of potash and black oxide of 
manganese in an iron retort and conducting the gas into a 

bag. 

2. Chlorine (Cl) is a great oxidizer and is generated by 
treating bleaching powder (chloride of lime) with sulphuric 
acid. 

3. Bromine (Br) is a good oxidizing agent. It is pur¬ 
chased in liquid form. It must never be uncorked but a 
few moments as it will combine with the orygen of the air 
and fill the room with the gas. When used it is added to. 
water and used as bromine water. 

4. Potassium permanganate (K2 Mn^ Og) is a power¬ 
ful oxidizing agent, and is much used in volumetric analyses 
of iron and many other metals. 

5. Potassium bichromate (Kg Crg O7) ^s a powerful ox¬ 
idizing agent largely used in volumetric analyses. 

6. Nitric acid (H N O3) is a very powerful and most 
convenient oxidizing agent. It is largely used for the oxi¬ 
dation of precipitates. Must always be used pure and kept 
in a dark place. 

7. Potassium chlorate (K Cl O3) is a great oxidizer used 
for the manufacture of the gas, also in fusion and in solu¬ 
tions. 

8. Sodium nitrate (Na N O3). Used as oxidizing agent 
in fusion. The potassium salt (K N O3) may be used for 
the same purpose as the sodium salt. 

9. Ammonium nitrate (N N O3) is a good oxidizer, 
and is easily decomposed when heated. 

EXERCISE ON 
REDUCING REAGENTS. 

1. How is hydrogen manufactured? 

2. What is the principal use of sulphuretted hydrogen 
gas? 


OXIDIZING REAGENTS 


38 

3. What is the use of sodium sulphide? 

4. What is the use and test of stannous chloride? 

OXIDIZING REAGENTS. 

1. How is oxygen prepared? 

2. How is chlorine gas prepared? 

3. In what way is bromine used? 

4. What is the principal use of permanganate of potas¬ 
sium? 

5. What is the principal use of potassium bichromate? 

6. How should nitric acid be used? 

7. For what is potassium chlorate used? 

8. What is sodium nitrate used for? 

9. What is ammonium nitrate used for? 


I 


GOLD AND SILVER BULLION 39 

CHAPTER VIL 

MELTING OF GOLD AND SILVER BULLION. 

For the determination of silver in silver bullion, or gold 
in gold bullion, the furnace and fuel may be the same. 
Coke or charcoal,or in some places stone coal, may be used. 
It should be free from dust and broken into small lumps 
the size of a hen's egg. Charcoal is best to start with . 

1. The black lead crucibles and covers should first be 
annealed by drying them for a day in a good oven, or by 
placing them in a furnace after melting and letting them 
cool down with it. Then before using insert crucibles and 
covers over a good fire until they are red-hot; they are then 
ready for use and may be placed when cold in the hottest 
fire without danger of fracture, which is sure to be the case 
if not annealed as above described. 

The metal to be melted, if in small quantities, may be put 
into the cold crucible (pot), then placed in the fire, resting 
on a piece of fire brick. 

2. Small crucibles with small lots of gold dust may be 
set into the fire with fragments of coke placed around them 
to keep them upright, and then covered. 

3. In melting large lots in large crucibles it is best to 
feed a part of the metal or gold dust with an iron scoop 
made for the purpose. 

4. Borax is added, the pot covered, and fuel placed 
around it. Retorted amalgam, especially silver, is porous 
and bulky, and the pot must be filled from time to time as 
it is melted down; sometimes such metal contains quick¬ 
silver and then the addition must be made before that in the 
pot is quite melted; otherwise spurting may occur. 

5. When the metal is all thoroughly melted and the slag 
formed by the borax floats thin on the surface, it must be 
removed. The skimmer is placed in contact with the slag 
to which it adheres. The skimmer is then withdrawn, 


40 MELTING OF GOLD 

pressed on the surface plate and dampened with water to 
cool and flatten the adhering slag. Occasionally dip it in 
water slightly to cool it and again touch the slag, rolling it 
upon the furnace plate, and so on until the slag is com¬ 
pletely removed from the surface of the metal. Replace the 
cover and in a few minutes it is ready to pour into the mold. 

6. The slag must be neither too thin nor too pasty; if 
the latter it may contain globules of the metal, and if the 
former it cannot be readily skimmed off. 

7. A small amount of bone ash may be used to thicken 
it . If too thick add a little borax. When all the slag has 
been skimmed off, the surface of the metal is bright, and it 
is ready for pouring. 

8. If the surface is covered with a skum it probably con¬ 
tains copper, iron, or sulphur. 

9. If rainbow colored rings are seen, it is owing to a 
small quantity of lead; if brilliant spots appear moving 
rapidly it shows that much lead is present. Therefore, fol¬ 
low closely these directions. 

10. First. If too thick add a lump of borax to absorb 
the base metallic oxides and when melted skim it off. If 
this does not purify it sulphur is probably present. 

Second. Add a mixture of borax, nitre, and pulverized 
glass; felt and then skim it off. If this treatment does not 
prove efficacious lead is probably present. 

. Third. Then add some cupels, allowing them to float 
on the metal for ten or fifteen minutes; they will absorb the 
lead. If much copper is present it is best to let it remain 
with the bullion in the bar, as it will make no difference in 
the determination of the silver or gold except that it will 
make it much harder. 

11. In melting gold and silver together or in melting 
gold dust alone it is important that the metals be well 
mixed. For this purpose the stirrer is used—a strip sawed 


AND SILVER BULLION 


41 


from an old plumbago crucible will do. While the melt¬ 
ing is in progress the stirrer is heated to redness and the 
metal thoroughly stirred before pouring into the mold; es¬ 
pecial attention must be paid to this if the metal is of any 
considerable quantity. With a small lot of. forty or fifty 
ounces it is unimportant, as it can be easily mixed by surg¬ 
ing it around in the pot by the tongs. 

13. For casting large lots in the mold, it is important 
that it be thoroughly smoked by mounting upon two brick¬ 
bats over a dish of burning rosin until the mold is well 
coated with soot; this insures a smooth bar if the mold is 
just merely warmed. In casting small bars of thirty to fifty 
ounces mere oiling of the mold is sufficient. 

14. In all cases to have a good cast it is necessary that 
the pour be continuous from the commencement to the 
finish. 

15. Sprinkle some charcoal powder on to the metal as 
soon as poured to burn off any oxides of iron and to pre¬ 
vent silver from oxidizing. 

16. When the bar is sufficiently cooled it is turned out 
of the mold, cooled in water, scoured, smoothed, if neces¬ 
sary, by hammering, and dried by warming it on the furn¬ 
ace cover; this is necessary, for a one-hundred ounce bar 
will absorb a penny weight of water in cooling. 

17. The bar is now ready for weighing and chipping. 
The chips are taken'from two diagonally opposite corners, 
one top and one bottom. The chisel is held between the 
thumb and fingers of the left hand so as to retain the chip. 

18. If the metal is malleable the chip can be taken in 
one piece, flattened on the anvil, then rolled out, cut in 
small pieces with the scissors for weighing. If the metal is 
brittle it is best to cut it in several small pieces to facilitate 
the weighing of the assay, and each sample placed on a 
separate piece of paper. 


42 


MELTING OF GOLD 


19. The number of the deposit is marked on the paper. 

20. One assay is made from each sample and if the two 
do not agree, and the third assay or “control” does not cor¬ 
rect the result, the bar is melted over and remixed. The 
sample must be large enough to allow several assays to be 
made of each, the residue being folded up in the paper with 
the number of the deposit marked thereon and kept for fu¬ 
ture reference. 

21. Each bar is finally stamped on the face, which was 
the bottom of the bar when cast, with the name and ad¬ 
dress of the assayer, the weight in troy ounces and hun¬ 
dredths, with the fineness, and the value in gold, or in both 
gold and silver, according to the character of the bullion. 

22. When gold predominates and is above 500 fine in 
that metal it is called a gold bar; when silver predominates 
and is above 500 in silver then it is termed a silver bar, and 
is stamped for both gold and silver. 

On delivery it is accompanied by a certificate stating the 
number of the deposit, the name of the depositor, the 
weight both before and after melting, the fineness, value in 
dollars and cents, charges, etc. Any globules which may 
remain in the pot, may be weighed together with the chips 
and added to the bar, and the value recovered according to 
the assay. 

23. The value stamped on the bar is the assay value. 
But the commercial value depends upon the market price 
for that description of bullion. 

A black lead pot should not be used more than four or 
five times with any considerable quantity of metal, as it is 
liable to part at the surface of the metal, spilling the metal 
into the grate and ash pit below. In this case the furnace 
must be opened and the fire left to die down and cooTxl. 
Then the metal may be recovered by washing the ashes and 
cinders. 


AND SILVER BULLION 


43 

24. It is often that the assayer has to treat small lots of 
base bullion or gold scrapings from plates. In such cases 
it can be refined by cupellation. A large cupel can be made 
with a large mold or sometimes the moistened bone ash 
can be packed into a roasting cHsh or in the bottom of an 
old crucible with holes drilled through it. When well dried 
and required for use it may be placed on the coals in the 
melting furnace, or better in the muffel if there is room for 
it. Add some lead to it and when that is melted add the 
impure gold and silver, and proceed with the cupellation 
as in other cases. 

An iron or tin ring or hoop can be used to make a large 
cupel by forcing the dampened bone ash into it and leaving 
it to dry. Use with the ring still on it. 

EXERCISE. 

1. How should a black lead crucible be treated before 
using? 

2. How would you melt small lots of gold or silver, say 
10 or 50 ounces? 

3. How would you treat large lots, say 40 or 50 pounds? 

4. What would you add to flux to clean it? 

5. How would you skim the borax slag from a lot of 
melted gold in a pot? 

6. If the borax slag is too thin what is added to thicken 
it? 

7. If so thick as to lose gold by skimming what would 
you do to thin it? 

8. What are the indications of impurities in tbe ' ' 

9. What might it be? 

10. What would you add to purify it, and how would 
you treat it? 

11. How would you treat a pot of melted gold and sil¬ 
ver to thoroughly mix it? 

12. How should small lots be treated? 


44 GOLD AND SILVER BULLION. 

13. How should the mold for casting the metal be 
treated ? 

14. What is requisite for casting a smooth bar? 

15. What would you use to cover the bar to prevent 
oxidization? 

16. What is the next step in treating the bar? 

17. How is the bar chipped after weighing? 

18. How is the chip treated if malleable? If not malle¬ 
able? 

19. What should be done with the remaining chips? 

20. If the parallel assays do not agree and the “control’^ 
proves false, what is to be done? 

21. How should the bar be stamped? 

22. When is it called a silver bar? A gold bar? 

23. What does the assay value of the bar show? 

24. How would you make a large cupel, and how would 
you refine a few ounces of metal in it? 


ASSAYING BULLION 45 

CHAPTER VIIL 
ASSAYING BULLION. 

1. The object in assaying bullion is to find out how 
many parts of it in one thousand consist of pure gold or 
silver; in other words how many thousandths f f it are gold 
and how many are silver. 

2. In writing or stamping the bar we use the decimal 
marks thus: gold .600 fine, silver .390 fine. Thousandths 
are always implied and are often called points. Add two 
points for cupellation loss. 

3. All gold bars are assayed with a delicate balance, and 
generally a half-gramme is taken for the assay, and the 
pure metal weighed in half-milligrammes. 

4. The weights are so arranged that a half-gramme rep¬ 
resents the thousand and the half-milligramme a “point” or 
a thousandth part of the half-gramme. 

5. In assaying a silver bar with a cheap balance one 
gramme may be used. Gold is never found in its pure state, 
but always alloyed with silver, and sometimes with copper; 
the bars are sometimes found to have a small amount of 
platinum which occurs in groins with the gold dust. 

6. In parting the silver from the gold the platinum is 
indicated by turning the nitric acid yellow or straw-color. 

7. It is indispensable when the silver is parted from the 
gold that there should he at least two parts of the silver to 
one of the gold. If more than three parts are used the gold 
would crumble to fine powder and be liable to cause a loss. 
Therefore we always aim to have the alloy two and one- 
half parts of silver to one of the gold. 

8. A good practical assayer can usually judge from the 
color and appearance of the sample, or from former experi¬ 
ence, about how much silver to add to obtain the right pro¬ 
portion in the alloy. An inexeprienced person would find 
it better to make a preliminary assay with tne addition of 


ASSAYING BULLION 


46 

enough silver to assure the success of parting, even though 
the gold may crumble to powder, then dry and weigh it, 
thereby determining the exact amount of silver to add to 
the assay proper. 

9. Preliminary Assay of a Gold Bar. Take one thou¬ 
sand of the sample and three and a half or four thousand of 
test silver and wrap it up in three or four thousand of sheet 
lead. Cupel under a strong heat. The bead is then 

’ cleaned, beaten by a hammer on an anvil to a flat plate, an¬ 
nealed to redness once or twice, parted, cupped, dried to a 
red heat and weighed. A mattress is used in parting on 
account of the large quantity of the metal. The approxi¬ 
mate is the fineness to which the two and one-half parts of 
silver is to be added to the assay proper. From this the 
quantity of silver already alloyed with the gold must be 
deducted. 

10. In case of very small bars this kind of assay will do 
if the gold be twice boiled in nitric acid and cupped with 
care to prevent loss, then deducting two points for sur¬ 
charge from the results found. 

11. It is not necessary to take 1,000 parts to make the 
assay just referred to; any amount will do from 100 to 1,000. 
Suppose we take .236 points and after assaying as above we 
get 233.2 points of fine gold we have only to add ciphers to 
the latter number and divide by the former to three places 
in the quotient which gives us .988 as the fineness. 

12. Where there is routine work in bullion assaying it 
is always best to follow one regular rule and weight of the 
thousand. 

13. If the gold obtained from the 1,000 of the sample 
weighs 924 the lost weight is that of the silver, except per¬ 
haps a few points of base metal, which need not be noticed 
in this class of assays. 

14. The bullion then contains 924 of gold and 76 of sil¬ 
ver in 1,000. Multiplying 924 by 2.5 we have 2.310 of sil- 


ASSAYING BULLION 


47 

ver required for the parting, of which quantity the bullion 
contains 76, leaving 2.234 to be added to make two and 
one-half parts of silver to one of gold. 

15. Assay Proper of Gold Bar. Weigh off one thou¬ 
sand chipped from the bar, or if the bar is a large one con¬ 
taining over $500, weigh out one thousand in duplicate 
chipped from diagonally opposite corners; add the two and 
one-half parts of pure test silver and about 3 to 4 points of 
copper. Envelope it in a small cone made of about three 
thousand of sheet lead, and roll up into a cornet. The lead 
for this purpose is usually kept on hand, ready made, and 
cut into about one and one-half inch squares. The weighed 
assay is transferred directly from the scale pan to the cornet 
by means of the pincettes. 

I weigh my test silver on a small open balance, sitting by 
the side of it, and having it always loaded with 1,800 of the 
half-gramme system. This weight stands for a gold alloy 
of 800 fineness, the other 200 being silver added to the 
1,800, making a total of 2,000, or 2.5 times 800. The cor¬ 
net is then placed on the tray with its respective number. 

16. The muff els are heated to a lignt redness and the 
assays are placed in them according to their regular order 
and number. The muffel door is then closed until the as¬ 
says are uncovered, when it is opened. If by any means 
the front cupels are not hot enough some hot coals may be 
placed in the front part of the muffel. 

17. A high heat should be kept up during the cupeling 
and especially at the close when the brightening takes 
place, because gold is less volatile than silver. 

If a silver assay is left in the muffel at a high heat after 
the lead has passed off it is liable to volatilize and all be 
found in the roof of the muffle. 

18. A gold assay will stand a much higher heat and may 
be left in the muffel until all are uncovered and then cooled 
without much precaution, as they are not so apt to sprout. 



48 


ASSAYING BULLION 


19. Copper is added to render the metal tougher and 
more malleable in lamination. No assay should be sub¬ 
mitted to the muffel unless the heat is sure to be main¬ 
tained to finish the work. For want of heat the assay may 
freeze or solidify, thus rendering it wholly unreliable. 

20. The cupel bead is cleaned with a good toothbrush, 
flattened on an anvil and annealed by heating to a dull red¬ 
ness in the muffel, and then passed througn the rollers un¬ 
til it is about two and one-half inches long. If it is hard 
and cracks on the edges anneal it again. At last, when 
finished, anneal again and roll it up into an open coil—this 
is called the cornet as well as the lead capsule—it is then 
placed in a three ounce mattress and gently boiled in one 
and one-half ounces of nitric acid, 26 Baume, for 
ten minutes. The acid is then poured off and replaced by 
a fresh quantity of acid of 32 Baume, adding a charred len¬ 
til, or a bit of charcoal will do, to keep it from bumping; 
boil for fifteen or twenty minutes. The acid is now poured 
off and the charcoal must go with it. 

21. The gold is washed in three waters, cupped and 
heated to redness in the muffel, cooled and weighed, and 
should be in one piece. The weighing of the gold should 
be less from a half to one point as a surcharge, owing to 
small traces of silver remaining with the cornet. 

22. The result of two assays as described above should 
agree within a quarter of a point in weight. 

EXERCISE. 

1. What is the object in assaying bullion? 

2. What expression would you use in writing or stamp¬ 
ing a bar of bullion? 

3. What weights would you use in weighing the cornet? 

4. When the half-gramme is used for 1,000 what does 
the milligramme represent? 

5. What may be used in assaying a silver bar? 


ASSAYING BULLION 


49 

6 . What is indicated when the acid turns straw-color 
in parting the silver from the gold? 

7. How inuch pure silver is recpiired to make a success¬ 
ful parting from the gold? 

8 . How would you determine the amount of silver to be 
added in parting? 

9. How would you make a preliminary assay? 

10. In what kind of bars would an assay of this descrip¬ 
tion answer? 

11. Having taken 236 points and obtained 233.3 
gold, how would you determine the fineness? 

12. What is the best method to adopt in routine work? 

13. If the gold obtained from 1,000 of the sample 
weighs 924, how much silver would you add to make two 
and one-half parts? 

14. Explain how you would arrive at the amount, in¬ 
cluding the silver already in the bar? 

15. What sized bars require duplicate assays, and how 
are the chips taken? 

16. How is the cupel prepared for placing the cornet 
into it? 

17. When is the most heat required? Why is a gold 
assay button less volatile than a silver one? 

18. Why are they less subject to sprouting? 

19. Why is co])])er added to the assay? 

20. How is the button treated after cupelling? What 
strength of acid is used for boiling it? 

21. After parting, how is the gold treated before weigh¬ 
ing? 

22. What is to be done when two assays from the same 
bar do not agree? 


50 BASE BULLION 

CHAPTER IX. 

ASSAYING OF DOREE BARS, BASE BARS, SIL¬ 
VER BARS, SILVER LEAD, ETC. 

1. All of these assays are generally conducted in a sim¬ 
ilar manner to that of a gold bar. But a preliminary assay 
is generally required. 

2. The Doree bar may need the addition of either gold 
or silver to produce a suitable alloy for parting. The gold 
should be absolutely pure, weighed and added to the 
weighed assay, and cupelled with the proper amount of 
lead. 

3. The difference between the weight of the bead and 
that of the assay less the gold added represents the base 
metal. 

4. The bead is flattened and parted like all other assays, 
and the weight of the cornet less that of the gold added 
with the proper amount of surcharge is the fineness of the 
gold; it is not always necessary to add gold: this is left to 
the judgement and experience of the assayer alone. 

5. When the bar is about half gold then it becomes 
necessary to add silver in place of the gold. If a prelimin¬ 
ary assay has been made and an approximate of gold and 
silver determined, then the silver may be added at once and 
cupelled and the silver determined by difference. 

6. In assaying of base bullion the assay sample is cu¬ 
pelled in duplicates. In case of impaire bullion each sample 
should be scorified with a little borax before cupelling. 

7. If the lead is very impure and contains a good deal 
of copper a little test lead will help the scorification. Some 
assayers prefer to scorify all samples before cupellation, 
contending that the loss of silver in scorification is less than 
the loss in cupellation. 

9. When a large amount of copper is present in a bar 
a larger amount of lead should be used. 


BASE BULLION 51 

9. Mitchell has given in the following table an idea of 
the proportion of lead required to separate copper from 

very convenient to refer to, 


gold by cupellation, which is 
especially when there is a lot 
and assayed: 

Gold in alloy. 

.900 

.800 

.700 

.600 

.500 

.400 

to 

.050 


of old jewelry to be melted 

Lead required. 

10 parts. 

16 parts. 

22 parts. 

24 parts. 

26 parts. 

34 parts. 


10. The above is supposed to be an alloy of gold and 
copper alone, but if half the copper were replaced with sil¬ 
ver then only half the above amount of lead would be re¬ 
quired to cupel it. 

11. In assaying a silver bar, which generally contains 
more or less copper, by cupellation, it is a good plan, after 
chipping and weighing your cornet, to also weigh out an 
equal amount of pure silver and cupel it with an equal 
amount of pure lead as that used with the cornet; cupel 
together in the same muffle and with the same heat as a 
check. The loss of pure silver by cupelling should be 
added to the assay proper as a loss by cupellation. 

12. I have known as high as 25 points to be lost by 
unskillful cupellation, nhich should never be more than 
from five to ten with careful work. 

13. Lead, copper, antimony, tin, bismuth, mercury, etc., 
are always calculated by per cent. 

14. Gold, silver, platinum, etc., are always calculated by 
the ounce troy. 

15. To find the value of a bar, multiply the troy ounces 
bv the gold fineness (stated in thousandths) which gives the 


52 


BASE BULLION 


weight of pure gold contained, the value of which is com¬ 
puted at $20.67 ounce. 

16. The weight of the bar multiplied by the silver fine¬ 
ness (stated in thousandths) gives the weight of pure silver 
contained. Silver is reckoned at $1.2929 per ounce. 

17. The above value of pure silver and gold multiplied 
by the fineness of the bar in each metal (stated in thou¬ 
sandths) gives the value per ounce of such bullion for each 
metal, and the weight of the bar multiplied by the respec¬ 
tive value per ounce, gives the value of the entire bar for 
each. It is well to make the calculation in both ways in 
order that the one may check the other. 

18. Again, the value of pounds and ounces avoirdupois 
may be computed by the aid of the following table, after 
multiplying the weight of the bar by the fineness in gold 
and silver respectively for the contained weights of the 
pure metals: 



Gold value. 

Silver value. 

One pound. 

.$30146 

$18.85 

One ounce. 

. 18.84 

1.17 

One-quarter ounce. 

. 476 

0.29 

One-eighth ounce. 

. 2.38 

0.14-J 

One-sixteenth of an ounce. 

. i-W 

074 


EXERCISE. 


1. Why is a preliminary assay more often required in a 
Doree or base bar than any other? 

2. Why is the addition of gold required? 

3. How would you determine the base metals in the 
assay? 

4. Is it always necessary to add gold? 

5. When the bar is about half gold and half silver what 
would you add? 

6. Would you make base bullion assays in duplicate? 
Why are they scorified? 







BASE BULLION 53 

7. In case the bead is very impure and contains much 
copper what would you do? 

8. Jf there is a large amount of copper present in the 
bar how would you treat it in assaying? 

9. What are Mitchell’s 'ables for cupelling gold or 
allov? 

10. When the alloy is half silver what proportion of 
lead is added? 

11. In assaying a silver bar by cupellation, how is it 
checked? 

12. How much loss of silver will take place with careless 
work ? 

13. What metals are calculated and reported in percent¬ 
ages? 

14. What metals are calculated by their ounce value? 

15. How would you find the value of a gold bar in troy 
ounces? 

16. How is the value of a silver bar found in troy 
ounces? 

17. Why is it necessary to calculate both? 

18. How would you make the calculation in avoirdu¬ 
pois pounds and ounces? 


54 


HUMID ASSAY OF 
CHAPTER X. 


HUMID ASSAY OF SILVER BULLION. 

This is the GayLussac method of determining the fineness 
of silver bullion, and beyond doubt is the most accurate 
method of assaying silver yet devised. It has been adopted 
in all the United States mints and assay offices, and in all 
the first-class private establishments in the United States. 

1. The principle depends upon the fact that silver in 
nitric acid solution is completely precipitated in the form of 
chloride by a solution of common salt. 

Suppose, for instance, that we wish to know the quantity 
of pure silver contained in a shilling. The coin is first dis¬ 
solved in nitric acid, by which means a bluish solution con¬ 
taining silver, copper, and probably other metals, is ob¬ 
tained. It is a known fact that chlorine combines with sil¬ 
ver in the presence of other metals to form silver chloride, 
which is insoluble in nitric acid. 

2. The proportion in which the combination takes place 
is 35.37 of chlorine to every 107.66 of silver; consequently, 
if a standard solution of pure sodic chloride is prepared by 
dissolving in water such a weight of salt as will be equiv¬ 
alent to 35.37 grains of chlorine (58.37 grains Na. Cl.) and 
diluting to the measure of 1,000 grains, every single grain 
measure of this solution will combine with 0.10766 grains 
of pure silver to form silver chloride, wmeh is precipitated 
to the bottom of the vessel in which the mixture is made. 

3. In the process of adding the salt solution to the sil¬ 
ver, drop by drop, a point is at last reached when the pre¬ 
cipitate ceases to form. Here the process must stop, be¬ 
cause we have arrived at a point where there is neither salt 
nor silver in the solution. On looking carefully at the 
graduated vessel (burette) from which the standard solu¬ 
tion has been used, the operator sees at once the number of 


SILVER BULLION 55 

grain measures which has been necessary to produce the 
complete decomposition. 

4. For example, suppose the quantity used was 520, 
grain measure, all that is necessary to be done is to multi¬ 
ply 520 by the coefficient for each grain measure, viz; 
0.1076, which shows the amount of pure silver present to 
be 55.95 grains. It must be understood that there are cer¬ 
tain necessary precautions in conducting the above process 
which I will endeavor to point out. 

5. These salt solutions can be made up of pure salt, but 
it is more troublesome to prepare pure salt and to measure 
pure water with perfect accuracy than to make a solution 
which approaches the required standard, and then to rec¬ 
tify it by an addition of salt or water as indicated by the 
result of an assay of pure silver of known fineness made 
with it. 

6. The easiest way in which to prepare the salt solution 
is first to make a saturated solution as hereinafter directed, 
and from this is made the normal solution of which 100 
c.c. will exactly precipitate 1,000 of pure silver, as after¬ 
wards described; and from the normal salt solution is made 
the decime salt solution, which is one-tenth as strong as 
the normal; consequently, i c.c. of it precipitates one point 
of silver. 

7. A decime silver solution is also prepared of which 
I c.c. contains one point of silver; consequently the two 
decime solutions are equivalent, volume for volume, each 
neutralizing the other. 

8. For the preparation of the saturated solution take 
about a pound of good table salt and dissolve it in about 
two quarts of water. Put the solution through a course fil¬ 
ter, and boil it down to a quarter of the original quantity, 
causing the greater part of the salt to be deposited. Pour 
off the liquid and wash the salt quickly before dissolving it. 


56 HUMID ASSAY OF 

Redissolve the salt in as little water as possible, and again 
evaporate until a little of the salt is again deposited. Cool 
the liquid and put it into a bottle. This is the saturated so¬ 
lution, and contains about 26.5 per cent of its weight of 
salt. 

9. To prepare the normal solution. For the gramme 
system take 2.08 volumes of the saturated solution and add 
97.92 volumes of pure water in any quantity required. For 
the grain system take 1.33 volumes of the saturated solu¬ 
tion and 98.66 volumes of water for any quantity required. 

10. If more convenient, take for the gramme system five 
parts, by any kind of weight, of saturated solution, and 189 
parts by weight of water, or one to 37-88. 

11. For the grain system, one part, by any kind of 
weight, of the saturated solution to 58.89 of water. 

12. To prepare the decime salt solution, use any vol¬ 
ume of the normal solution diluted with 9 such volumes of 
water. Measure with the large pipette 100 c.c. of water, 
which pour into the appropriate bottle; remove 10 c.c. of 
the water by means of the small pipette, and replace it by 
an equal volume of the normal solution. Mix, by shaking; 
this small quantity is for correcting the standard of the 
normal; after this has been done a new decime solution 
must be prepared if the error of the normal was considera¬ 
ble, and a larger quantity wiii be required. 

To prepare it, measure one litre (1,000 c.c.) of water, or 
weigh 1,000 grammes at 60 degrees Fahr.; remove 100 c.c. 
of the water and replace it by 100 c.c. of the corrected 
normal solution by means of the large pipette. 

13. Standardizing the Normal Solution. A thousand 
of pure silver is dissolved in about 10 c.c. of nitric acid, 
about 30 Baume, in a bottle of clear glass which will con¬ 
tain about 200 c.c. To facilitate the action the l)ottle is 
placed in a vessel containing warm water. 


SILVER BULLION 57 

When the silver is dissolved the red fumes are blown out 
of the bottle by means of a bent glass tube. As soon as 
the assay has cooled, 100 c.c. of the normal solution are 
added by means of the pipette and the bottle wrapped with 
a dark cloth to keep the light from the silver chloride as 
much as possible, and the stopper, previously dipped in 
pure water, put in. 

The bottle is then briskly shaken for a few minutes, 
which causes the precipitate to curdle and settle rapidly, 
leaving the liquid perfectly clear. When the liquid has 
cleared, the stopper is removed and laid in a clean place 
so that the moistened part will touch nothing. A c.c. of 
the decime salt solution is then poured into the bottle. If 
immediately afterwards a cloudiness appears in the liquid it 
is evident that the normal solution is weak, because 100 c.c. 
of it has not precipitated 1,000 of silver. The liquid must 
be again cleared by shaking and another c.c. of the decime 
• salt solution added, and so on, until no further cloudiness 
is produced. 

A record must be kept of each c.c. used of the decime so¬ 
lution, but the last one is not counted because it gave no 
cloud, and the one before the last was probably not all re¬ 
quired, so it is counted as half. Supposing that 7 c.c. caused 
precipitation, but the eighth did not, only 6^ must be 
counted. 

14. It now appears as though i,oo6-| points of silver had 
been present in the solution, but it is known that there 
were 1,000, because that quantity was weighed ; the normal 
solution is, therefore, 6^ points weak, and requires a cor¬ 
responding addition of salt. The quantity of salt required 
is found by the following: 

Rule. Multiply the weight or measure of salt or sat¬ 
urated solution used in making the entire quantity of nor¬ 
mal solution by the number of c.c. of decime salt solution 



V 


58 HUMID ASSAY OF 

which w’ere necessary to complete precipitation, and divide 
by 1,000. The result is the weight or measure of the re¬ 
quired addition. 

As a portion of the normal has been withdrawn for the 
test for making the decime solution, the quantity thus 
found may be corrected by the deduction of a correspond¬ 
ing percentage: but it is not worth while, unless either 
many tests have been made, or but a small quantity of nor¬ 
mal has been prepared, for even though the addition of 
salt required may be considerable, it is evident, from the 
fact that the normal is wxak, that the saturated solution 
used was less strong, or the salt less pure, than w^as sup¬ 
posed, so that the added quantity will have the same de¬ 
ficiency in proportion. If dry salt was used in making the 
normal, and consequently will be used also in the correc¬ 
tion, the required quantity should be dissolved in some of 
the original normal poured into a beaker for that purpose, 
and then mixed with the main stock, the beaker being • 
rinsed with a very little water and tnat also added. Another 
test must then be made, and, if necessary, another correc¬ 
tion. 

If the first addition of i c.c. of decime salt solution pro¬ 
duces no precipitate, it is known that the normal is either 
correct or too strong; to ascertain which, add 2 c.c. of de¬ 
cime silver solution. One of these is consumed in neutral¬ 
izing the c.c. of decime salt previously added; hence only 
one is counted. Shake down and add another c.c. of de¬ 
cime silver; if this produces no cloud, the normal is correct 
within at most a point, and may be accepted, for it is need¬ 
less to make it perfect, for reasons which wdll appear here¬ 
after. If a cloud is produced, shake dcwm again, and con¬ 
tinue adding decime silver solution and shaking down until 
the last added c.c. causes no cloudiness; then, as with the 
salt, reject the last c.c. and half of the preceding one. Sup- 




SILVER BULLION 


59 


posing that, in all, 5 c.c. have been used, we reject one of 
the first two added, because it only counteracted the c.c. 
of decime salt previously added; we also reject the last, be¬ 
cause it gave no precipitate, and the one before the last we 
count as a half c.c. Thus we have 2J c.c. of decime silver 
solution which were necessary to complete the decomposi¬ 
tion of the salt in 100 c.c of the normal. Apparently only 
997 i points of silver were dissolved, but we know that 
1,000 were so; consequently the normal is 2^ points too 
strong, and water must be added. The quantity of water is 
found by the following: 

15. ‘‘Rule. Multiply the quantity, by weight or meas¬ 
ure, of water used in making the entire quantity of normal 
solution by the number of c.c. of decime silver solution 
which were necessary to complete the assay, and divide by 
1,000. The result is the quantity of water to be added to 
the normal solution. Mix thoroughly. 

A correction for the percentage of the normal which has 
been used is more necessary in this case; still it is hardly 
worth the trouble, because, if the error of the normal is 
large, a second rectification will probably be required, and 
if it is small, the difference will not be perceived. After 
mixing, test again; when the normal is sufficiently exact, 
make a new decime salt solution. 

16. Examples. The normal solution was made with 5 
pounds avoirdupois of saturated solution, and a test assay 
on pure silver required c.c. of decime salt solution to 
finish; then 5 times 8-J makes 42.5, and this divided by 1,000 
gives 0.0425 pounds of saturated solution to be added to the 
normal. A pound avoirdupois is equal to 7,000 grains 
Troy, and, multiplying this by 0.0425, we have 297.5 grains. 

Again the normal solution was made with 189^ pounds 
of water, and proves to be too strong, a test assay requiring 
5^ c.c. of decime silver solution to finish; then, 189.5 rnul- 
tiplied by 5.5 gives 1,042.25, which, divided by 1,000, gives 
1.04 pounds of water to be added.” 

If dry salt has been used, or if the saturated solution or 


6 o 


HUMID ASSAY OF 


the water had been measured by volume, the same kind of 
calculation would give the required result in terms of the 
weight or measure used. 

When the normal solution is within about a point of 
being correct, it may be accepted, perfect accuracy being 
needless on account of the changes of volume produced by 
alterations of the temperature, for which a correction must 
be made as hereafter directed, and includes any inaccuracy 
in the standardizing; for the present, however, the solution 
will be supposed to be exact. 

17. The Assay.—For the sake of convenience, a c.c. of 
either of the decime solutions will be called a point of sil¬ 
ver or a point of salt, as the case may be; also 100 c.c. of 
the normal solution will be called a thousand of salt. 

One thousand of salt requires 1,000 of silver, and such a 
weight of the bullion is taken for the assay as contains, as 
nearly as may be, 1,000 of silver. This being dissolved and 
1,000 of salt added, we then proceed, by means of the de- 
ci’me solutions, to ascertain how many points of silver more 
or less than 1,000 the assay contains. Knowing the weight 
taken, and having found the weight of the contained silver, 
it is easy to find by proportion what weight of silver 1,000 
of the bullion contains, which is its fineness. 

In order to be able to take the required weight of the 
sample we must have an approximate knowledge of its 
silver fineness; this is obtained by means of a preliminary 
assay by cupellation, and, if necessary, parting. As we 
know from experience that there is a certain loss of silver in 
the cupellation, we add to the result of the preliminary 
assay such a number of points as the judgment may dictate. 
From the approximate fineness thus obtained we calculate 
the weight which must be taken in order that the assay may 
contain nearly 1,000 of silver: Thus, suppose the cupella¬ 
tion (and parting) gave a silver fineness of .864, and we add 


SILVER BULLION 6i 

3 points for loss, making .867, then, as 867 are to 1,000 so 
are 1,000 to 1,153.4, and we weigh ofl 1,154; hence the 

Rule.—Divide 1,000,000 by the number of points of ap¬ 
proximate fineness; the result is the desired weight in 
points. 

Dissolve the quantity of the sample in about 7 c.c. of 
nitric acid, in the manner directed for the standardizing of 
the normal solution; cool, add 1,000 of salt, shake down 
and add a point of salt. If a cloud is produced, proceed to 
complete the assay with salt, as in testing the normal solu¬ 
tion, keeping a record of the number of points added, 
finally rejecting the last and half of the preceding one. 
Suppose 1,154 of the bullion to have been taken, and that 
three points of salt have given a precipitate, the fourth 
none, we have then found that 1,154 points of the bullion 
contain 1,002^ points of silver; to find the fineness, we take 
the proportion, as 1,154 are to 1,002.5 so are 1,000 to 869.7; 
as not less than a point is usually stamped on a bar, we may 
say the bullion is .869 fine. 

If the first added point of salt gives no precipitate, add a 
point of silver to neutralize it, shake down and add another; 
if this produces no precipitate, the assumed fineness was 
correct; if otherwise, proceed to finish with silver in the 
same manner as with salt ; then rejecting the first point be¬ 
cause it was required to counteract the point of salt, and the 
last because it gave no result, also half of the preceding one 
because it was probably only required in part, deduct the 
remainder of the added points from 1,000, which leaves the 
number of points in the assay. If, as before, 1.154 of the 
bullion were taken, and one added point of salt gave no pre¬ 
cipitate, and four successive points of silver gave a precipi¬ 
tate, the fifth none, then it is known that 1,154 of the bullion 
contain 9984 of silver, and as 1,154 are to 998.5 so are 1,000 
to 865.25, or the bullion is .865 fine. Hence to find the 
fineness, the following; 


62 


HUMID ASSAY OF 


18. Rule.—Multiply the points of silver found by i,ooo, 
and divide by the points of bullion taken. 

Greater exactitude can be attained by finishing" with half 
points, but for ordinary purposes it is not necessary. The 
gold fineness is found in the preliminary assay by cupella- 
tion and parting. 

It is better to finish with salt than with silver, so the 
weight of bullion taken for the assay should be such as to 
contain a little more, rather than less than i,ooo of silver; 
and if it is not so, and is found to contain less, a number of 
points of silver may be added at once, so as to make more 
than 1,000; the assay is then finished with salt. An ac¬ 
count must be kept of the silver and salt added, the one —, 
the other —. If more than eight points of salt or silver are 
required to finish, it is advisable to make another assay on 
the basis of the result found. 

The last trace of precipitate is somewhat difficult to dis¬ 
cern. It can be seen best by looking obliquely upward 
through the liquid, while holding the bottle toward the 
light. Another help is to have a black background, for 
which a black felt hat answers. The writer and some oth¬ 
ers have found it advantageous to have the assay solution 
tinged by copper; the white silver chloride shows very 
plainly in the blue solution. An experienced assayer, on 
observing that the first added point of salt causes a consid¬ 
erable precipitate immediately, will add several more points 
before shaking down, being able to judge about how many 
will be required; he can also tell, almost with certainty, 
when another point will be without effect. 

In case the furnace is not fired, a preliminary assay may 
be made by means of the blowpipe. It is not necessary 
that any special weight be taken, therefore select a piece of 
bullion which may weigh about loo, more or less; weigh it, 
cupel it with lead before the blowpipe flame, not allowing 


SILVER BULLION 


63 

the flame to touch the metal, hut heating the cupel around 
it by directing the point first on one side and then on an¬ 
other, weigh the bead, part and weigh the gold if there is 
much; then as the weight of the silver is to that of the assay, 
so is 1,000 to the weight of the l)ullion to be taken for the 
volumetric assay, to which a few points may be added for 
the loss, which is likely to be greater, at least in inexperi¬ 
enced hands, than in the muffle. The gold may be calcu¬ 
lated for 1,000 on the same principle, but it may be better 
to dissolve 1,000 of the bullion in nitric acid and weigh the 
gold from that, the only difficulty being that it is likely to 
be in finer powder than when parted from a bead which has 
been purified from base metal by cupellation. 

An excellent preliminary, and even an accurate assay, 
may be made by means of a Mohr burette. Dissolve 1,000 
of the bullion in the usual manner. Charge the burette 
very accurately with normal solution, and run that into the 
assay bottle, first in larger, then in smaller quantities, finally 
drop by dro]r, shaking down each time, until the last drop 
or two produces no precipitate. The value of a drop may 
be ascertained by noting how many drops lower the float 
I c.c. The last addition, which produces no precipitate, is 
not counted, and the preceding is counted for half its value. 
The burette should be read after each addition toward the 
end; it should be of 100 c.c. capacity, graduated to tenths, 
and furnished with a float. If, by accident, an excess of salt 
solution is run in, add ten or more points of decime silver 
solution, making a note of it; and then finish with salt. If 
preferred, the assay may be finished with decime salt solu¬ 
tion from a second burette, or from the small pipette, but 
with care this will not be necessary, as the normal can be 
measured to less than a point. The number of c.c. neces¬ 
sary for complete precipitation, multiplied by ten, is the 
fineness, provided no addition of decime silver has been 
made; otherwise that must be deducted. Special care must 


64 HUMID ASSAY OF 

be taken that no air remains in the jet of the burette when 
charged, to which end it is best to partly charge it from 
below, by suction, and then to fix it in the stand and fill it 
from above. 

Correcting the Assay.—It has thus far been supposed 
that the normal solution was accurately standardized, so 
that 100 c.c. would exactly precipitate i,ooo of silver. In 
order that this may be the case, it must not only have been 
made of correct strength, but it must always be used at the 
same temperature, which cannot well be. For this reason 
a check assay is made, on pure silver, which each set of 
bullion assays, a number of which can be conducted at the 
same time, and are corrected according to the error found, 
whether that is caused by expansion or contraction of the 
solutions, owing to a change of the temperature, or from 
inaccurate standardizing. 

The result of an assay of pure silver should be i,ooo fine; 
if it gives more or less, the assay of each sample of bullion 
must be corrected in proportion to its fineness. This is 
arrived at with sufficient exactness by adding to, or sub¬ 
tracting from, the number of points found, in the assay, the 
amount of the error of the check, before calculating the 
fineness of the bullion. Thus: If the result of the check is 
2^ points above i,ooo, that quantity must be deducted; if 
below, added. Suppose the check-was points high, and 
1,154 of bullion gave 1,005^; we deduct 2 \ from that, leav¬ 
ing 1,003, from which we then calculate the fineness, which 
is 870. If the check had been low, we should have added 
ij, making 1,007 in 1,154, and the fineness would have 
been .873. 

“Suppose the alloy bas a standard of about 900 thous¬ 
andths, we have the following proportion: 

900 thousandths: 1,000 of alloy:.: 1,000 thausands:x= 

nil.I. 


SILVER BULLION 


65 

If that weight be now taken to ascertain the standard of 
the alloy, it may be found, for instance, that to the measure 
of one-thousandth of salt it is yet necessary to add 4 thous¬ 
andths of salt to precipitate the whole of the silver; that is 
to say, that iiii.i of alloy really contain 1,004 of silver. 
From this result the real standard of the alloy may be found 
to be 903.6, by the following equation: 

iiii.i: 1004:: 1000:X =903.6. But such calculations, 
however simple, should be avoided where numerous daily 
assays are made, not only on account of the time consumed, 
but still more from the errors to which such operations are 
necessarily exposed. Fortunately, all these inconveniences 
may be avoided by the use of tables, which entirely free the 
assayer from calculation. 

‘‘Wishing in weighing the alloy to avoid fractions of 
thousands, and only making use of tenths and half-tenths 
of thousands, the weight of alloy increases, starting from 
a gramme, from 5 to 5 thousands, and the corresponding 
standard for each of these weights has been sought, all con¬ 
taining one gramme of pure silver. Thus the weight 1,020 
of alloy, in which there are 1,000 of silver and 20 of copper, 

corresponds to the standard 980.39, obtained by the pro¬ 
portion—1020: 1000:: 1000 :X =980.39. 

“On this principle are formed the first and second col¬ 
umns of the table marked Salt. The first contains the 
weight of each alloy, and the second its corresponding 

standard. The following columns, i, 2, 3, etc., milli¬ 
grammes of copper less. 

“Another table, constructed in the same manner as the 
preceding, and marked nitrate of silver, gives the standard 
of the alloy when, under the weight given in the first col¬ 
umn, it contains 1, 2, 3, etc., milligrammes less silver, and 
as much more copper. Thus, for example, an alloy of the 
weight of i,C20 (1,000 silver and 20 copper) has for its 
standard 98' .4 in both tables. If it always contains in the 


66 


HUMID ASSAY OF 


same weight 4 more silver and consequently 4 less copper, 
its standard would be 984.3, and would be found in the 
‘Salt’ table at the intersection of the column 4, and the hori¬ 
zontal line 1020. If, on the contrary, it contains 4 less of 
silver and 4 more of copper, its standard will be 976.5, and 
will be found in the ‘Nitrate of Silver’ table, at the intersec¬ 
tion of the column 4, and the horizonal line 1020.” 


SILVER BULLION 

TABLE A.—FOR DECIMAL SALT SOLUTION 


67 


Tables for Determining the Standard of any Silver Alloy 
by Employing an Amount of Alloy, Always Approx¬ 
imately Containing the Same Amount of Silver. 

COMMON SALT. 


Weight of 
Alloy 
Assayed, 
in 

Milli¬ 

gramme. 

0. 

1 . 

2 . 

3 . 

4 . 

5 . 

6 . 

7 . 

8 . 

9. 

10 . 

Cubi 

c cent 

imete 

spon< 

rs of 
a to i 

decin 
i con 

jrmal 
;ent c 

salt 
if fint 

solut 

i SllV( 

on a( 
sr of- 

ided 

3orre- 

1000 . 

1000.0 











1005 . 

995.0 

996.0 

997.0 

918.0 

999.0 

1000.0 






1010 . 

990.1 

991.1 

992.1 

9 ) 3.1 

994.1 

995.0 

996.0 

997.0 

998.0 

999.0 

1000.0 

1015 . 

985.2 

986.2 

987.2 

9 ? 8.2 

989.2 

990.1 

991.1 

992.1 

993.1 

994.1 

996.1 

1020 . 

980.4 

981.4 

982.4 

9 ^ 3.3 

984.3 

985.3 

986.3 

987.2 

988.2 

989.2 

990 . t 

1025 . 

975.6 

976.6 

977.6 

9 : 8.5 

979.5 

980.5 

981.5 

982.4 

983.4 

984.4 

985.4 

1030 . 

970.9 

971.8 

972.8 

9 73.8 

974.8 

975.7 

976.7 

977.7 

978.6 

979.6 

980.0 

1035 . 

966.2 

967.1 

968.1 

9 59.1 

970.0 

971.0 

972.0 

972.9 

973.9 

974.9 

975.8 

1040 . 

961.5 

962.5 

963.5 

9 54.4 

965.4 

966.3 

967.3 

968.3 

969.2 

970.2 

971.1 

1046 . 

956.9 

957.9 

958.8 

9 ') 9.8 

960.8 

961.7 

962.7 

963.6 

964.6 

965.5 

966.6 

1050 . 

952.4 

953.3 

954.3 

9 ') 5.2 

956.2 

957.1 

958.1 

959.0 

960.0 

960.9 

961 .i 

1055 . 

947.9 

948.8 

949.8 

9 '> 0.7 

951.7 

952.6 

953.5 

954.5 

955.4 

956.4 

957 .S 

i 060 . 

943.4 

944.3 

945.3 

9 t 6.2 

947.2 

948.1 

949.1 

950.0 

950.9 

951.9 

952.8 

1065 . 

939.0 

939.9 

940.8 

941.8 

942.7 

943.7 

944.6 

945.5 

946.5 

947.4 

948.4 

1070 . 

934.6 

935.5 

936.4 

937.4 

938.3 

939.3 

940.2 

941.1 

942.1 

943.0 

943.8 

1875 . 

930.2 

931.2 

932.1 

933.0 

933.9 

934.9 

935.8 

936.7 

937.7 

938.6 

939.6 

i 080 . 

925.9 

926.8 

927.8 

928.7 

929.6 

930.6 

931.5 

932.4 

933.3 

934.3 

935.1 

1085 . 

921.7 

922.6 

923.5 

924.4 

925.3 

926.3 

927.2 

928.1 

929.0 

930.0 

930.9 

1090 . 

917.4 

918.3 

919.3 

930.2 

921.1 

922.0 

922.9 

923.8 

924.8 

925.7 

926.6 

1095 . 

913.2 

914.2 

915.1 

916.0 

917.0 

917.8 

918.7 

919.6 

920.5 

921.5 

922.4 

iloo . 

909.1 

910.0 

910.9 

911.8 

912.7 

913.6 

914.5 

915.4 

916.4 

917.3 

918.2 

1105 . 

905.0 

905.9 

906.8 

997.7 

908.6 

909.5 

910.4 

911.3 

912.2 

913.1 

914.0 

1110. 

900.9 

901.8 

902.7 

993.6 

904.5 

905.4 

906.3 

907.2 

908.1 

909.0 

909.9 

ills . 

896.9 

897.8 

898.6 

899.5 

900.4 

901.3 

902.2 

903.1 

904.0 

904.9 

905.8 

1120 . 

892.9 

893.7 

894.6 

895.5 

896.4 

897.3 

898.2 

899.1 

900.0 

900.9 

901.8 

1125 . 

888.9 

889.8 

890.7 

891.6 

892.4 

893.3 

894.2 

895.1 

896.0 

896.9 

897.8 

1130 . 

885.0 

885.8 

886.7 

887.6 

888.5 

889.4 

890.3 

891.1 

892.0 

892.9 

893.8 

1135 . 

881.1 

881.9 

882.8 

883.7 

884.6 

885.5 

886.3 

887.2 

888.1 

889.0 

889.9 

1140 . 

877.2 

878.1 

878.9 

879.8 

880.7 

881.6 

882.5 

883.3 

884.2 

885.1 

886.0 

il 45 . 

873.4 

874.2 

875.1 

876.0 

876.9 

877.7 

878.6 

879.5 

880.3 

881.2 

882.1 

1150 . 

869.6 

870.4 

871.3 

872.2 

873.0 

873.9 

874.8 

875.7 

876.5 

877.4 

878.3 

1155 . 

865.8 

866.7 

867.5 

868.4 

869.3 

870.1 

871.0 

871.9 

872.7 

873.6 

874.5 

1160 . 

862.1 

862.9 

863.8 

864.7 

865.5 

866.4 

867.2 

868.1 

869.0 

869.8 

870.7 

il 65 . 

858.4 

859.2 

860.1 

860.9 

861.8 

862.7 

863.5 

864.4 

865.2 

866.1 

866.9 

1170 . 

854.7 

855.6 

856.4 

857.3 

858.1 

859.0 

859.8 

860.7 

861.5 

862.4 

863.2 

1175 . 

851.1 

851.9 

852.8 

853.6 

854.5 

855.3 

856.2 

857.0 

857.9 

858.7 

859.6 

1180 . 

847.5 

848.3 

849.2 

850.0 

850.8 

851.7 

852.5 

853.4 

854.2 

855.1 

855.9 

1186 . 

1190 . 

843.9 

840.3 

844.7 

841.2 

845.6 

842.0 

846.4 

842.9 

847.3 

843.7 

848.1 

844.5 

848.9 

845.4 

849.8 

846.2 

850.6 

847.1 

851.5 

847.9 

852.3 

848.7 

1195 . 

836.8 

837.7 
834.2 

830.7 

838.5 

839.3 

840.2 

841.0 

841.8 

842.7 

843.5 

844.3 

845.2 

1200 . 

833.3 

835.0 

835.8 

836.7 

837.5 

838.3 

839.2 

840.0 

840.8 

841.7 

1205 . 

829.9 

831.5 

832.4 

833.2 

834.0 

834.8 

835.7 

836.5 

837.3 

938.2 

1210 . 

826.4 

827.3 

828.1 

828.9 

829.7 

830.6 

831.4 

832.2 

833.1 

833.9 

834.7 

1215 . 

823.0 

823.9 

824.7 

825.5 

826.3 

827.2 

828.0 

828.8 

829.6 

830.4 

831.3 

1220 . 

819.7 

820.5 

821.3 

822.1 

822.9 

823.8 

824.6 

825.4 

826.2 

827.0 

827.9 

1225 . 

816.3 

817.1 

813.8 

810.5 

818.0 

818.8 

819.6 

820.4 

821.2 

822.0 

822.9 

823.7 

824.5 

1230 . 

813.0 

814.6 

815.4 

816.3 

817.1 

817.9 

818.7 

819.5 

820.3 

821.1 

1235 . 

809.7 

811.31 

808.1 

812.1 

813.0 

813.8 

814.6 

815.4 

816.2 

817.0 

817.8 

1240 . 

806.5 

807.3 

804.0 

800.8 

797.6 

808.9 

809.7 

810.5 

811.3 

812.1 

812.9 

813.7 

814.5 

1245 . 

803.2 

804.81 

805.6 

806.4 

807.2 

808.0 

808.8 

809.6 

810.4 

811.2 

1250 . 

800.0 

801.61 

802.4 

803.2 

804.0 

804.8 

805.6 

806.4 

807.21 808.0 

1255 . 

796.8 

798.41 

799.2 

800.0 

800.8 

801.6 

802.4 

80 . 3.2 

804.0 

804.8 












































































































68 HUMID ASSAY OF 

TABLE B.—FOR DECIMAL SILVER SOLUTION 


Tables for Determining the Standard of Any Silver Alloy 
by Employing an Amount of Alloy, Always Appox- 
imately Containing the Same Amount of Silver. 

NITRATE OP SILVER. 


Weight of 
Alloy 
Assayed, 
in 

Milli¬ 

gramme. 

0 . 

1 . 

2 . 

3 . 

4 . 

5 . 

6 . 

7 . 

8 . 

9 . 

10 . 

Cubii 

3 cent 

imetei 

respo 

'S of 
nd to 

decinc 
a coi 

)rmal 

itent 

silve 
of fin 

r soli 
e silv 

ition 
er of- 

addec 

cor- 

. 

1000 . 

1000.0 

999.0 

998.0 

997.0 

996.0 

995.0 

994.0 

993.0 

992.0 

991.0 

990.0 

1005 . 

995.0 

994.0 

993.0 

992.0 

991.0 

990.0 

989.0 

988.1 

987.1 

986.1 

985.1 

1010 . 

990.1 

989.1 

988.1 

987.1 

986.1 

985.1 

984.2 

983.2 

982.2 

981.2 

980.2 

1015 . 

985.2 

984.2 

983.2 

982.3 

981.3 

980.3 

979.3 

978.3 

977.3 

976.4 

975.4 

1020 . 

980.4 

979.4 

978.4 

977.4 

976.5 

975.5 

974.5 

973.5 

972.5 

971.6 

970.6 

1025 . 

975.6 

974.6 

973.7 

972.7 

971.7 

970.7 

969.8 

968.8 

967.8 

966.8 

965.8 

1030 . 

970.9 

969.9 

968.9 

968.0 

967.0 

966.0 

965.0 

964.1 

963.1 

962.1 

961.2 

1035 . 

966.2 

965.2 

934.2 

963.3 

962.3 

961.3 

960.4 

959.41 

958.4 

957.5 

956.5 

1040 . 

961.5 

960.6 

959.6 

958.6 

957.7 

956.7 

955.8 

954.8 

953.8 

952.9 

951.9 

1045 . 

956.9 

956.0 

955.0 

9 o 4.1 

953.1 

952.1 

951.2 

950.2 

949.3 

948.3 

947.4 

1050 . 

952.4 

951.4 

950.5 

949.5 

948.6 

947.6 

946.7 

945.7 

944.8 

943.8 

942.9 

1055 . 

947.9 

946.9 

946.0 

945.0 

944.1 

943.1 

942.2 

941.2 

940.3 

939.3 

938.4 

1060 . 

943.4 

942.4 

941.5 

940.6 

939.6 

938.7 

937.7 

936.8 

935.8 

934.9 

934,0 

1065 . 

939.0 

938.0 

937.1 

936.1 

935.2 

934.3 

933.3 

932.4 

931.4 

930.5 

929.6 

1070 . 

934.6 

933.6 

932.7 

931.8 

930.8 

929.9 

929.0 

928.0 

927.1 

926.2 

925.2 

1075 . 

930.2 

929.3 

928.4 

927.4 

926.5 

925.6 

924.7 

923.7 

922.8 

921.9 

920.9 

1080 . 

925.9 

925.0 

924.1 

923.1 

922.2 

921.3 

920.4 

919.4 

918.5 

917.61 

916.7 

1085 . 

921.7 

920.7 

919.8 

918.9 

918.0 

917.0 

916.1 

915.2 

914.3 

913.4 

912.4 

1090 . 

917.4 

916.5 

915.6 

914.7 

913.8 

912.8 

911.9 

911.0 

910.1 

909.2 

908.3 

1095 . 

913.2 

912.3 

911.4 

910.5 

909.6 

908.7 

907.8 

906.8 

905.9 

905.0 

904.1 

1100 . 

909.1 

908.2 

907.3 

906.4 

905.4 

904.5 

903.6 

902.7 

901.8 

900.9 

900.0 

1105 . 

905.0 

904.1 

903.2 

902.3 

901.4 

900.4 

899.5 

898.6 

897.7 

896.8 

895.9 

1110 . 

900.9 

900.0 

899.1 

898.2 

897.3 

896.4 

895.5 

894.6 

893.7 

892.8 

891.9 

1115 . 

896.9 

896.0 

895.1 

894.2 

893.3 

892.4 

891.5 

890.6 

889.7 

888.8 

887.9 

1120 . 

892.9 

892.0 

891.1 

890.2 

889.3 

888.4 

887.5 

886.6 

885.7 

884.8 

883.9 

1125 . 

888.9 

888.0 

887.1 

886.2 

885.3 

884.4 

883.6 

882.7 

881.8 

880.9 

880.0 

1130 . 

885.0 

884.1 

883.2 

882.3 

881.4 

880.5 

879.6 

878.8 

877.9 

877.0 

876.1 

1135 . 

881.1 

880.2 

879.3 

878.4 

877.5 

876.7 

875.8 

874.9 

874.0 

873.1 

872,3 

1140 . 

877.2 

876.3 

875.4 

874.6 

873.7 

872.8 

871.9 

871.0 

870.2 

869.3 

868.4 

1145 . 

873.4 

872.5 

871.6 

870.7 

869.9 

869.0 

868.1 

867.2 

866.4 

865.5 

864.6 

1150 . 

869.6 

868.7 

867.8 

867.0 

866.1 

865.2 

864.3 

863.5 

862.6 

861.7 

860.9 

1155 . 

865.8 

864.9 

864.1 

863.2 

862.3 

861.5 

860.6 

859.7 

858.9 

858.0 

857 . i 

1160 . 

862.1 

861.2 

• 860.3 

859.5 

858.6 

857.8 

856.9 

856.0 

855.2 

854.3 

853.4 

1165 . 

858.4 

857.5 

856.6 

855.8 

854.9 

854.1 

853.2 

852.4 

851.5 

850.6 

849.8 

1170 . 

854.7 

853.8 

853.0 

852.1 

851.3 

850.4 

849.6 

848.7 

847.9 

847.0 

846.1 

1175 . 

851.1 

850.2 

849.4 

848.5 

847.7 

846.8 

846.0 

845.1 

844.3 

843.4 

842.5 

1180 . 

847.5 

846.6 

845.8 

844.9 

844.1 

843.2 

842.4 

841.5 

840.7 

839.8 

839.0 

1185 . 

843.9 

843.0 

842.2 

841.3 

840.5 

839.7 

838.81 838.0 

837.1 

836.3 

836.4 

1190 . 

840.3 

849.5 

838.7 

837.8 

837.0 

836.1 

835.3 

834.5 

833.6 

832.8 

831.9 

1195 . 

836.8 

836.0 

835.1 

S 34.3 

833.5 

832.6 

831.8 

831.0 

830.1 

829.3 

828.4 

1200 . 

833.3 

832.5 

831.7 

830.8 

830.0 

829.2 

828.3 

827.5 

826.7 

825.8 

825 0 

1205 . 

829.9 

829.0 

828.2 

827.4 

826.6 

825.7 

824.9 

824.1 

823.2 

822.4 

821 6 

1210 . 

826.4 

825.6 

824.8 

824.0 

823.1 

822.3 

821.5 

820.7 

819.8 

819.0 

818 2 

1215 . 

823.0 

822.2 

821.4 

820.6 

819.7 

818.9 

818.1 

817.3 

816.5 

815.6 

814 8 

1220 . 

819.7 

818.8 

818.0 

817.2 

816.4 

815.6 

814.7 

813.9 

813.1 

812.3 

811 5 

1225 . 

816.3 

815.5 

814.7 

813.9 

813.1 

812.2 

811.4 

810.6 

809.8 

809.0 

808 8 

1230 . 

813.0 

812.2 

811.4 

810.6 

809.8 

808.9 

808.1 

807.3 

806.5 

805.7 

804 9 

1235 . 

809.7 

808.9 

808.1 

807.3 

806.5 

805.7 

804.9 

804.0 

803.2 

802.4 

801 6 

1240 . 

806.5 

805.6 

804.8 

804.0 

803.2 

802.4 

801.6 

800.8 

800.0 

799.2 

798*4 

1245 . 

803.2 

802.4 

801.6 

800.8 

800.0 

799.2 

798.4 

797.6 

796.8 

796.0 

795 2 

1250 . 

800.0 

799.2 

798.4 

797.6 

796.8 

796.0 

795.2 

794.4 

793.6 

792 8 

792 0 

1255 . 

796.8 

796.0 

795.2 

794.4 

793.6 

792.8 

792.0 

791.2 

i 790.4 

789.6 

788.8 
































































































































SILVER BULLION 
EXERCISE. * 


69 


1. What is the principal of the humid assay? 

2. What are the combining weights of chlorine and 
silver, and what is the molecular weight? 

3. When a salt solution is dropped into a silver solu¬ 
tion until no precipitate forms, what does it indicate? 

4. Suppose you had dropped salt solution into a silver 
solution until no more p.p. takes place, and your burette 
records 520, how would you caluculate the amount of sil¬ 
ver in solution in the parts per thousand? 

5. Which is the best way to prepare the salt solution, 
by weight or measurement? 

6. How many salt solutions is it necessary to make, 
and what are they termed? 

7. What other solution is necessary, and what is it 
termed ? 

8. How would you prepare a saturated solution of 
common salt? 

9. How would you prepare the normal salt solution? 
For the gramme system; by measure? 

10. How by weight by the gramme system? 

11. How by the grain system by weight? 

12. How would you prepare the decime salt solution? 

13. How would you standardize the normal salt solution 
with the 1,000 of pure silver? 

14. If your normal salt solution is 6-| too weak, what is 
the rule for correcting it? 

15. Suppose we find that the decime silver solution is 
2 i c.c. too strong, what is the rule for correcting it? 

16. Suppose the normal salt solution was made with 5 
pounds avoirdupois of saturated solution, and a test on pure 
silver required 8^ c.c. of decime salt solution to finish it, 
what is the rule of correction? 

17. What is a c.c. of decime, of salt or silver solution 
called ? 

18. What is the rule to find the fineness of a silver bar 
when the determination is made in points? 


70 


CONCLUSION PART ONE 
CONCLUSION TO PART 1 . 


In the assaying of bullion it is necessary to save the res¬ 
idue of the chips from the bar, wrap them in paper care¬ 
fully, and mark the number of the bar thereon; should there 
be any reclamation or error in the assay, you have them to 
refer to for a re-assay. If the bar proves to be short in the 
value stamped upon it the assayer must pay the difference, 
if he wishes his assay to pass in the market; though the 
error may have been made in the mint, the private assayer 
has to suffer the loss. On the other hand, if a bar is 
stamped too low, the purchaser of the bar is the gainer and 
it is never heard of. An instance is in my knowledge 
where a reclamation was made from a bar which had been 
re-melted and assayed in a private office in San Francisco. 
A short time afterwards the melter of the bar was arrested 
for embezzlement from the melting pot and substituting 
half-dollars to make up the weight. No reclamation should 
be made or allowed, except on a mint certificate, and while 
their assaying is but little, if any, better than that of some 
private offices, it is necessary to have a place to submit all 
errors for correction. 




PART II. 



1 



INTRODUCTION PART TWO 
INTRODUCTION TO PART 11 . 


73 


Among the many processes of assaying metals and ores 
there is but little new matter to be added to the various pro¬ 
cesses now published and practiced. My object, therefore, 
throughout this work, is not so much to present any new 
methods, as to abbreviate, compile, copy, and quote some of 
the best now in use, divesting them of much superfluous mat¬ 
ter and rendering them simple and plain to the beginner; 
also to arrange it in such form that the study and practice 
can be taken up in systematic order and in sections, so that 
when the student has passed through the work and has had 
the practical illustrations, *he cannot fail to understand the 
principles of the work he is conducting. 

It is not my intention to here introduce all the different 
methods for the determination of the various metals in ores, 
but to give one or two of the most simple and accurate, thus 
enabling him to understand the main points in the various 
processes and digest it in his mind, rather than to dig it out 
of a voluminous chapter of reading matter. It is intended 
for the beginner and to assist the practical miner and pros¬ 
pector. For those who have a knowledge of algebra and 
higher mathematics, I would recommend Cook’s Philos¬ 
ophy, Fresenius, and Francis Sutten on Volumetric Anal¬ 
ysis. But in the present work I feel confident that the stu¬ 
dent will find many short-cuts to obtain results which have 
heretofore been considered extremely difficult. I know 
that it is not nearly so clear and plain as it ought to be and 
hope at some future time to revise it, with some improve¬ 
ments, but to those interested I would say, examine the 
book and point out the errors, this being my first attempt to 
simplify a work of which I have long felt the need, and 1 
hereby submit it to the professors and teachers of the vari¬ 
ous institutions of learning for their criticism. 


74 


PREPARATION OF 

PREPARATION OF THE ORE SAMPLE. 


Accurate sampling of the ore is essential, for if the sam¬ 
ple does not truly represent the lot from which it was taken, 
the subsequent assay will be valueless. 

It is one of the most absurd customs, and one the most 
frequently practiced, to make the one-stone assay. It can¬ 
not be too severely ridiculed, for it would be just as reason¬ 
able for a geologist to land on a strange coast and pro¬ 
nounce the whole country similar to what he saw under his 
feet, or as correct in judgment for a burglar to enter a hard¬ 
ware store during the night and bring the first thing he 
handled to light and say the whole store was stocked with 
axes, as to say the one stone was a true sample of the vein 
cf ore. 

There are many methods in vogue for sampling the ore 
from a mine, among which may be mentioned the hand 
sampling, mechanical sampling, quartering, halving, split, 
shovel, channeling sampling, etc. It makes very little dif¬ 
ference which of these methods are adopted so long as the 
ore or pulp is thoroughly mixed. 

The Taylor rock crusher is a good one for small lots. 
After the ore has been put through it, it must then be passed 
through a coarse sieve of forty mesh to the lineal inch; then 
spread m a layer and divide it with a spatula into quarters * 
reject two quarters and sweep cleanly oflf the table. The 
other two quarters are again mixed and pulverized either in 
Buck’s patent mortar or bucking board. A common iron 
mortar will do, although it is slower work. The ore must 
be pulverized finely enough to pass through a sixty-mesh 
sieve, some advocate a hundred-mesh sieve, but I see no ad¬ 
vantage in it, as the pulp when assayed should be thor¬ 
oughly fused with the fluxes added and converted into a 
glass. 

After passing the pulp through the last sieve, it should be 


THE ORE SAMPLE 


75 

spread out heaped, quartered, and sampled as before until 
the sample is gradually reduced in quantity to a few ounces, 
which is then spread out upon glazed paper or oil cloth. 
Lift the edges of the cloth or paper, thus causing the ore to 
roll upon itself, and finally heap it up, flatten it out with a 
spatula, and weigh out the charge from different parts of 
the pulp. It is indispensable that the sample be thoroughly 
mixed, and if the pulp is damp it must be dried before sam¬ 
pling. 

It often happens that samples of pulp come for assay in 
bottles corked and sealed, as a check upon other assayers or 
smelting works who are purchasers of the ore. In all such 
cases it is supposed that the ore has been properly sampled 
before bottling. In such instances it is proper to first test 
the sample in order to know what dressing to use for the 
assay, and to determine the percentage of sulphurets, if it 
contains any. To do this, weigh out a small amount of the 
pulp, place upon a watch crystal and pan it out; dry, and de¬ 
termine the percentage of sulphurets and treat the ore ac¬ 
cordingly. If the sample is damp, determine the amount of 
moisture and report it in the percentage. 

All such samples should be carefully treated by weighing 
cut three charges and assaying them with the fluxes re¬ 
quired. The result is reported from the mean of the three 
assays, for it matters not how fine you may mix or pulver¬ 
ize the ore, it is almost impossible to get two assays 
to run exactly alike, especially in gold ores; and since there 
will be always be a dollar or two a ton difference it is always 
best to make three or more assays and take the mean of the 
lot as the true result. 

New and clean crucibles must always be used for the 
work, and all implements used in powdering and sifting 
must be cleaned lest some former ore may contaminate it. 
Sometimes a mere wiping out of the mortar with a cloth 


76 PREPARATION OF 

will do, but if a rich ore has been used, all must be cleaned 
by grinding some glass or barren sand before pulverizing 
the sample. Keep a tag with number and mark of each 
sample separate in pans and be careful not to get the num¬ 
bers mixed, or all your work is worthless. 

The following notes are imperative. Ores to be assayed 
by the wet method should be sampled as above stated be¬ 
fore being submitted to the solvent action of the re-agent. 

1. In filtering large quantities of liquid use a whole 
sheet of paper, fold it three or four times, and cut straight 
across at a distance from the corner equal to the distance in 
diameter of the required filter, then turn it to an arc of a 
circle, open to the twice folded paper so that it shall form a 
cone having one thickness on the one side, and three on the 
other. 

2. Small filters can be purchased of various sizes and 
qualities to fit the funnels in use. When not on hand, cut 
from the sheet and fit to funnel as above stated. All filters 
and funnels should be adapted to the bulk of the precipitate. 

When a substance is to be weighed on the filter, the filter 
must be counterposed by another, or its weight known, in 
order that the net weight of the substance may be obtained. 

3. The filter must be dried prior to use, at the tempera¬ 
ture at which the substance is afterwards to be dried on it. 

4. In filtering, fill the filter often, not waiting for it to 
drain. 

5. In washing the substance on the filter, let it drain be¬ 
fore each addition of water. 

6. It is generally best to let a precipitate settle before 
filtering, then filter the liquid first as far as practicable. 

7. It is a good plan in filtering silica, lime, etc., after the 
first decantation to add water to the precipitate; stir it; let 
settle; sometimes boil, and again settle and filter off several 
times before bringing the precipitate on the filter. 


THE ORE SAMPLE 


77 

8. As a general rule in pouring from one vessel to 
another, hold a glass rod to the lip, and let it run down the 
rod and against the side of the filter or other receiver. 

9. In filtering from the filter to the filtrate, do not allow 
the liquid to fall splashing into the receiver, but let it trickle 
down its side; even if the filtrate is not required, it is not 
clean work, 

10. There are several ways of determining when the 
washing 01 the precipitate is completed ; if the filtrate was 
acid, the washings must cease to redden blue litmus paper, 
except when directed to wash with acidulated water. 

II. If alkaline, they must not discharge the color of 
reddened litmus paper. If the water used be pure (as it 
should be), a drop from the filter, evaporated on a piece of 
glass or platinum foil will leave no film, or only a slight 
speck. 

12. The filter and its contents may be dried in the funnel. 
The drying should be continued until two weighings, after 
thorough cooling in the dessicator, give the same result. 

13. In removing the dried precipitate from the filter, 
open it carefully and invert on a sheet of glazed paper, 
loosening the p.p. carefully, and scraping it off. Then 
double it and rub the surfaces together; lay it flat, and brush 
it with a rather hard brush; heat, cool, and weigh. 

14. Fold and burn the filter on a platinum wire in the 
flame until the filter is completely incinerated, and add the 
ash to the precipitate. 

15. When the precipitate is to be dried and weighed on 
the filter, two filters of exact weight, one to counterbalance 
the other, must be arranged. Place one filter accurately 
within the other, and both in the funnel; when the filtration 
and washing are completed the filters and precipitate are 
dried together, and the weighing and the empty filter is put 
on the w’eight pan. But for fear some of the substance may 


PREPARATION OF 


78 

pass through the first filter, it is better to wet and dry the 
empty filter by itself. 

16. In some cases, like chloride of silver or sulphate of 
lead, it may be precipitated and the water drawn off, dried 
and weighed in the porcelain crucible, and the weight of 
the crucible deducted from the total weight gives the weight 
of the precipitate. 

17. In volumetric assays always use the Mohr burette, 
fitted in suitable stands with clamps. In all accurate work, 
use the float as an indicator. 

18. When beakers are used for boiling, a sand bath must 
be used, and in using the glass rod, never drop it in the 
beaker. You will surely crack it if you do. But very gently 
reach the bottom of the beaker and let it rest against the 
side. 

19. Never put cold water into a hot dish, but always 
heat and cool gradually. 

20. Wash all glassware and dishes after using. Vessels 
used which have contained chlorine should be washed sev¬ 
eral times in warm water; a wet ball of paper is a good thing 
to clean wide-mouthed bottles. No work'is complete un¬ 
til every article has been washed and cleaned. 

EXERCISES. 

1. How are large quantities of liquid filtered? 

2. How is the net weight of a substance weighed on a 
filter obtained? 

3. At what temperature is the filter dried? 

4. What is said of filling the filter? 

5. How is a substance washed on the filter? 

6. Should a precipitate settle before filtering? 

7. How are silica, lime, etc., filtered? 

8. What is the general rule in pouring from one vessel 
to another? 


THE ORE SAMPLE 


79 

9. What is the method of filtering from the filter to the 
filtrate? 

10. How do you determine when the washing of the pre¬ 
cipitate is completed? 

11. Should any film be left when a drop from the filter 
is evaporated on a piece of glass? 

12. How long is the drying process continued? 

13. How is the dried precipitate removed from the filter? 

14. What is added to the precipitate? 

15. How do you prepare for drying and weighing the 
precipitate on the filter? 

16. How do you proceed in cases like chloride of silver 
or sulphate of lead? 

17. What burette is used in volumetric assays? 

18. How is the glass rod used? 

19. What is said of heating and cooling? 

20. What is said in regard to the care of all glassware 
and dishes? 

WEIGHING THE CHARGE. ' ' 

1. The pulp scales should have pans with handles at¬ 
tached so that they can be taken from the scales and emp¬ 
tied into the mixing mortar. 

Put the weights on the left hand pan and weigh the pulp 
accurately. After a little practice it will not be necessary 
to weigh the fluxes, except in some cases of nitre or flour. 

2. I prefer the measuring of the principal fluxes in all 
cases. I have a tin measure with handle like a spoon which 
holds one and one-half ounces of bi-carbonate of soda, an¬ 
other which holds one ounce of pulverized borax, another 
Vv'hich holds one ounce of litharge, and another which holds 
250 grains of salt, and I find them very convenient and 
much quicker than weighing. 

3. These can all be constructed on the assay ton system, 


8o WEIGHING THE CHARGE 

and are much more sensible and convenient than either 
ounces or gram. 

Where only proportions are required the term parts will 
be used, as will grains or grammes. 

The sign for assay ton is A. T. (See article on calculating 
the assay.) 

A UNIVERSAL FLUX. 

4. A universal flux may be made up for any and all 
kinds of ores consisting of the following ingredients and 
parts, but of course if sulphates are to be assayed without 
roasting, a due proportion of nitre must be added, and 
sometimes iron nails may be added with advantage. 

3i| pounds bicarbonate soda. 

1 pound pulverized borax. 

U pounds litharge. 

320 grains of flour. 

This proportion, thoroughly mixed, makes an excellent 
flux for all carbonates or free milling ores, and by using 
four and one-half to six parts of the flux with one part of 
the ore will give from 150 to a 200 grain button of lead. If 
a larger button is required, add a little more of a reducer. 
I prefer to mix a large quantity of the above flux and keep 
it in a box all prepared for work. The main thing is to get 
the ingredients thoroughly mixed, which can usually be 
done by mixing them pretty thoroughly in a wedgewood 
mortar, then passing them through a No. 40-mesh sieve. 
The flux can then be measured or weighed. 

MIXING THE CFIARGE. 

5. The best way is to first measure or weigh out the 
flux and place it in a wedgewood mortar. Then weigh out 
the ore, place it on top of the flux, and mix it with a pestle 
in the mortar. Then pour it into a crucible with a large 
open tin funnel, covering with salt. 


WEIGHING THE CHARGE 8i 

6 . Ihe assay should not more than two-thirds fill the 
crucible on account of the charge swelling when heated. 

7. The assay should not be packed or pressed down in 
the pot; if this be done, some of the substance is liable to 
be wasted, being blown out by the sudden and forcible es¬ 
cape of the gas. 

8 . Crucibles which have been used for rich ores should 
not be used for poor ones; and for important assays they 
should never be used, new and clean ones always being 
taken. 

9. The same applies to the use of scorifiers. A second¬ 
hand crucible will answer for the determination of lead 
alone very well where traces of gold are unimportant. 

ASSAY OF LITHARGE. 

10. Whenever a lot of litharge is purchased for use ii. 
should be assayed to determine the amount of silver it con¬ 
tains, although litharge is now prepared quite free from sil¬ 
ver for assay purposes. 

IT. The litharge of commerce may be used with advant¬ 
age, for it holds small traces of silver and prevents it from 
sinking into the cupel. 

12. The readiest way to make the assay of litharge is to 
])lace in the crucible: 

Litharge.4 A. T. 

Flour.i-io A. T. 

Soda . I A. T. 

. 4 nd cover with salt ; melt quickly. When cooled, clean and 
cupel the button. It is better to make parallel assays as 
above and determine the amount of silver residue after cu¬ 
peling. In all assays of ore made of this litharge the amount 
of silver should be deducted, and it is well to part the silver 
buttons for gold, which should not be present. If so, the 
litharge should be rejected. 





82 WEIGHING THE CHARGE 

TO FIND THE OXIDIZING POWER OF NITRATE 

OF POTASH. 

13. It is only necessary to note the weight of the lead 
obtained in the assay of litharge, and to the same charge 
add a known weight of nitrate of potash, say 20 or 40 grains, 
and note the loss of lead or weight of lead button so ob¬ 
tained, and divide the loss of lead by the weight of nitre 
added, which will be generally be three and a half to one, or, 

in other words, one gramme of nitre will oxidize three and 
one-half grammes of lead, generally. 

CRUCIBLE ASSAYS. 

14. C. H. Aaron divides the crucible assays into tvro 
systems, which he says may be applied to any ore, but are 
best adapted to certain cases. In either case the gold and 
silver is collected by the means of lead, from which they are 
afterwards separated. 

15. In the first system an excess of litharge is used to 
oxidize the base metals, except the lead required for the col¬ 
lection of the gold and silver. 

16. But most invariably a preliminary assay is neces¬ 
sary; it is a good method, especially in the assay of telurium 
ores, but otherwise I see no special advantage in it. 

17. It is very destructive to crucibles, and expensive in 
the use of litharge, and I see no special advantage in making 
the two systems, as much depends upon the intelligence and 
experience of the assayer. 

18. In Mr. Aaron’s second system or “nail assay,” lith¬ 
arge is not used as a flux for the gangue, but simply as a 
source of lead, and only so much of it as may be necessary 
for the purpose of dressing the charge, and obtaining the 
proper sized button, in collecting the gold and silver in the 
assay, and this is the only object in assaying all ores. 

19. It is advantages that all the base metals, except lead,. 


WEIGHING THE CHARGE 


83 

should be oxidized. Antimony sometimes passes more or 
less into the lead, and ores containing much antimony 
should not be assayed by this method, as it passes into the 
lead, causing the cupel to crack. 

20. If the ore contains copper it will be reduced and 
contaminate the botton, unless sulphur or arsenic be pres¬ 
ent to combine with it. 

21. In many cases sulphur may be added to a copper ore 
with advantage, and here again the assayer must be the 
judge whether it be necessary or not. 

22. In all cases of assaying rebellious ores for silver it is 
best to make a small assay as a preliminary test, then a 
larger one for a more accurate determination. 

23. Ores containing a high percentage of copper pyrites 
and speiss are better assayed by special methods. 

24. Both crucible and scorification assays are in general 
use, and both have their advocates, but that depends largely 
upon which they have been taught in learning their business. 
In Colorado, where the ores are rich in silver, the scorifi¬ 
cation is best, and I believe generally adopted. 

25. On the Pacific Coast the crucible assay is now 
largely adopted, and I believe gives better results, owing to 
its allowing larger quantities to be taken for the assay, and 
hence a larger button of gold obtained for weighing than in 

the scorification assay, where only a small quantity can be 
taken, resulting in a small button, which introduces a 
source of error in weighing and calculating the results. 

26. It frequently happens with ores containing sulphur- 
ets and copper that a larger button of lead is produced than 
necessary, and it may be hard and brittle. In all such cases 
it is better to scorifv the lead button down with the addition 

of test-lead, but in removing the button from the slag great 
care should be exercised that no particles of the button be 
lost. It is better to leave some slag with it than suffer anv 

less. 


84 


WEIGHING THE CHARGE 


27. In making up the charge it must be remembered 
that sulphur, arsenic and anitmony are reducing agents, and 
that ferric oxide and carbonate act as oxidizing agents, 

28. Nitre is the principal oxidizing agent used; but 
when used a preliminary assay should b e made to know 
how much to add, as sulphur, arsenic and antimony are re¬ 
ducers, and from the amount of lead they have reduced 
from litharge it can be easily calculated how much nitre to 
add to counteract their oxidizing power and give the proper 
sized button for cupellation. But when nitre is added care 
should be taken to heat it up gradually during fusion to pre- 
,vent loss in boiling over, when the fusion is complete. The 
assay should be allowed to remain in the furnace a few min¬ 
utes before pouring. 

29. In making cupels from dry bone ash, moisten it with 
carbonate water to make it adherent. 

30. The cupels should be dried a few days before using, 
and they should weigh about 18 grammes. 

31. When used they should be placed in the muffle and 
allowed to become hot before the button is dropped into 
them. 

32. In making a large number of assays use great care 
to have the cupels marked and numbered to correspond 
with the ore used. 

33. When cupelling commences under a good heat, 
open the muffle door to allow free access of oxygen, which 
greatly assists the cupellation. 

34. Never let the button cool or freeze in the cupel and 
attempt to finish it at some other time. Throw it away and 
do the work over. 


EXERCISES. 

I. Eor large work would you use weight or measures 
for flux? 


WEIGHING THE CHARGE 85 

2. Which is the most convenient and quickest way to 
work? 

3. What can you say of the assay ton? 

4. How is the universal flux made up, and what are its 
parts? 

5. How would you mix the charge? 

6. How much would you place in the crucible? 

7. Would you pack it down, or merely tap it to settle it? 

8. In what case would you use a second-hand crucible, 
if at all? 

9. How w^ould you charge a scorifier? 

10. How would you first treat a new lot of litharge? 

11. What advantage has the litharge of commerce? 

12. How would you assay litharge to determine the 
amount of silver it contains? 

13. How would you assay nitre to determine its oxidiz¬ 
ing power? 

14. Describe the two systems of crucible assays of C. H. 
Aaron. 

15. What is the first system? Explain it. 

16. What is the special advantage of this kind of assay? 

17. What are the disadvantages of this kind of assay? 

18. What is the second system of Aaron? 

19. What are its advantages? 

20. In the last case, if copper is present m the ore, what 
would be the effect? 

21. When can sulphur be added to advantage in fluxing 
ore? 

22. Why is it best to make a preliminary assay? 

23. How would you treat ores containing a high per¬ 
centage of pyrites? 

24. Which is preferred, crucible or scorifiers assays? 

25. Why IS the crucible mostly used on the Pacific 

Coast? 


86 


CRUCIBLE ASSAY FOR 

27. What must be remembered in making up a charge? 

28. Why do you make a preliminary assay before using 
nitre? 

29. How are cupels made from dry bone ashr 

30. What should a cupel weigh? 

31. How is the muffle prepared for the button? 

32. What care must be exercised when making a large 
number of assays? 

f 

33. What is the use of oxygen in cupellation? 

34. If the button becomes cool, what must be done? 

CRUCIBLE ASSAY FOR GOLD AND SILVER. 

t 

1. In ores carrying sulphurets of any kind the 
beginner should make a series of preliminary assays for 
the purpose of experiment, and of calculating the amount 
of reducers or oxidizers necessary for the charges. He will 
soon acquire the knowledge of the various ores so that he 
will be able to make the charge without a preliminary assay. 

2. An experienced workman can generally judge what 
to do; the writer rarely makes a preliminary assay, but in 
doubtful cases dresses the assay according to his judgment, 
with more or less of the various fluxes according to the na¬ 
ture of the gangue, with an addition of nitre or an extra 
dose of argole or flour, as the case may be. This is difficult, 
however, when the ore consists of a mixture, oxidizer and 
reducer, such as oxide of iron or copper glance. 

PRELIMINARY ASSAY. 

3. In case a preliminary assay is required, it may be 
made as follows: Consider whether the ore is likely to be 
a reducer. (That it contains sulphurets, or an oxidizei*: 
that it carries much red oxide of iron-black oxide of man¬ 
ganese, black or blue oxide, or green carbonate of copper, 
red lead or chromate.) 

4. If it is a reducer, take one-tenth A. T. of ore and five 


GOLD AND SILVER 


87 

A. T. of litharge; mix in a crucible, cover with salt, and melt 
with care that no coal fall in; the weight of the resulting 
button above O. L of an A. T. multiplied by 2.5 is the 
w^eight of nitre required in an assay of i A. T. of the ore; of 
course if a half-ton assay, take half that quantity, etc. 

5. If the button weighs much less than O. i of an A. T., 
the deficit multiplied by ten times the fraction of an assay 
ton representing the quantity of flour which would bring 
down one A. T. of lead from the litharge is the weight of 
flour to be used in an assay of one A. T. of the ore. 

6. This can all be done with grains or grammes as well 
as with A. T. weights. The main point to remember is that 
one part of nitre is equal to the oxidation of three and one- 
half to four parts of lead, according to its purity, or an 
equivalent of sulphurets; and one part of flour reduces from 
twelve to sixteen parts of lead from litharge. 

DRESSING THE CRUCIBLE ASSAY FOR GOLD 

AND SILVER ORES. 

7. The universal flux will generally do for all free mill¬ 
ing ores, but for ores carrying a large amount of silver, 
Mitchell gives one general formula for all gold and silver 


ores as follows: 

Ore . I part. 

Litharge . 5 parts. 

Soda . I part. 

Borax glass .i part. 


With salt to cover, another part of ]:)orax over that, and re¬ 
ducer (argole or flour)-or oxidizer (nitre), if needed, in ac¬ 
cordance with the indication given by a preliminary assay. 

8. The objections apply in a less degree to this as to the 
exclusive use of litharge as a flux as proposed by Aaron. 
It is a well conceded fact that in assaying sulphuret ores, a 
large amount of litharge as a flux is necessary for the col- 






88 


CRUCIBLE ASSAY FOR 


lection of all the silver, but not so necessary for the collec¬ 
tion of the gold. 

9. In a majority of cases two or three parts of litharge 

is sufficient. It may be necessary to alter the proportion of 
the other fluxes which the student will be enabled to do by 
a careful study of their action, remembering always that 
soda is a flux for quartz, borax for earths and metallic ox¬ 
ides, as is also the glass formed by soda with quartz, and 
litharge a flux for all. • 

10. The student will soon learn to rely on his judgment 
in equalizing the above fluxes to suit his ore for the collec¬ 
tion of all the silver. In any event, he can always fall back 
on his “nail assay” for ores carrying little sulphurets. 

11. Ores containing quartz, clay, lime, iron, oxide, with 
say ten per cent of sulphurets, the following formula will do: 


Ore. 

.I 

part. 

Litharge. 

. 3 

parts. 

Soda . 

.I 

part. 

Dried borax. 

.I 

part. 

Flour . 

.1-12 

part. 


Salt to cover; melt quickly; keep in furnace five minutes af¬ 
ter it is well melted. 

12. It is important in all cases that the soda and borax 
be well dried before using to keep from boiling over. If the 
ore is nearly all quartz the borax may be reduced and the 
soda increased, or litharge may be used instead. 

13. On the other hand, if earthy matters or metal oxides 
predominate, the soda may be reduced and the borax in- 
^icdsecl. Borax glass is always preferable. 

14. If the button obtained is too large it may be scorified 
down to a suitable size, say 200 grains, or if very important 
it is better to make a new assay and gauge your flux accord- 
ingly. 

15. It is important that the slag be thoroughly oxidized, 
retaining no vestige of sulphurets. 







GOLD AND SILVER 89 

The different kinds of sulphurets require different propor¬ 
tions of litharge to effect complete oxidation as follows: 
Only a small part of the litharge is reduced to lead. This is 
the only case where no nitre is used, and the oxidation takes 
place with litharge alone. It is an expensive assay, how¬ 
ever, and destructive to the crucible, and may be resorted to 
only where great accuracy is required in the determination 
of silver. 

16. An ore carrying ten per cent of iron pyrites would 
require fifty parts of litharge, therefore it would be best to 
use the smallest amount of ore possible to get the true re¬ 
sults from it. In any event it is always best to make a pre¬ 
liminary assay with the universal flux. 

• 17. If much copper is in the ore it is better to use a large 

amount 01 litharge in the preliminary assay, than to use the 
universal flux; it will convert the copper into a red oxide 
with no danger of forming green slag. 

18. One way in which to get rid of all difficulty as to the 
proportion of nitre is to use enough to completely oxidize 
every constituent of the ore; heat it well, and when flowing 
smoothly, roll up twenty grains of charcoal in a bit of paper 
and drop it into the molten assay, throw on top of it a little 
dry salt; keep it in the furnace five minutes, then tap it and 
pour it into the mold. The following formula will do for 


this kind of an assay: 

Ore . I part. 

Litharge. 8 parts. 

Soda. 2 parts. 

Borax . 2 parts. 

Nitre . 2 parts. 

Ground Glass. 2 parts. 


19. This would require a large-sized crucible; heat 
gently. When flowing smoothly add one-sixth part of char¬ 
coal in small lumps. When the assay flows smoothly under 
a good heat, shake the pot in the fire and pour. 








90 CRUCIBLE ASSAY FOR 

A still better way in which to make the assay for gold and 
silver ores containing much copper is to treat the weighed 
assay sample with hot nitric acid until the copper is dis¬ 
solved; filter and wash. 

20. To the filtrate and washing add hydrochloric acid or 
a solution of common salt as long as it gives a precipitate; 
collect the precipitate on a separate filter and wash it. The 
whole of the silver will be on the filters; that portion which 
existed in the ore as chloride, iodide, or bromide, on the 
first filter; the remainder on the second is also converted 
into chloride of silver. 

21. It would not answer to add salt or hydrochloric acid 
during the treatment of the ore, because the proper quan¬ 
tity cannot be known, and an excess would cause the gold 
to be dissolved and lost. 

22. Dry the two filters with their contents and dress the 
charge according to the amount of sulphur it may contain 
by adding nitre if required. In adjusting the flour or nitre 
it must be remembered that the filters will act as reducers 
unless they have been completely burnt to an ash in drying, 
which can be done on a roasting dish in the muffle. Cover 
with salt and melt in the usual way. 

23. Assays made in this way are quite clean, and a 
larger amount of ore can be used, as it is greatly reduced 
by the acid treatment. 

24. For concentrated pyrites, the following dressing 
given by Mitchell is suitable and will generally answer; 


Ore . . . 

Nitre .. 
Litharge 
Soda . . 
Glass . . 


I part. 
1.7 parts 
8. part. 
1.2 parts 
I part. 


Cover with salt. The litharge may be lessened as the 
proportion of soda and glass is increased. Glass is better 







GOLD AND SILVER 


91 

to add than precipitated silica, recommended by some, be¬ 
cause it is more fusible. 

25. The universal flux will suffice in 75 per cent of all 
the ores that have come to my office in the past ten years. 
But when not at hand the following dressing will do for 
most ores: 


Ore. 


Litharge. 

. parts. 

Soda . 


Borax . 

. ^ part. 

Flour . 


Iron. 

. 3 nails. 


Salt to cover. Leave in a strong heat for about twenty 
minutes. The nails are to free the lead from sulphur. 
When the ore contains a large quantity of pyrites, add a 
little nitre; if the ore contains much copper, sulphur or 
arsenic. The silver may fall short, but the gold will not. 
In no case should there be any distinct matter above the 
button, but all the metal sulphides should be blended in a 
black slag. 

26. Any amount of examples may be given for the 
dressing of the assay, but it is better that the student make 
his own experiments, and, above all, to learn and know the 
use of each substance added, and the function it performs. 

MELTING IN a CRUCIBLE. 

There are so many furnaces in use that it is impossible 
to give any positive instruction as to the melting. In large 
establishments the melting is done in a muffle furnace; 
others in a combination or open furnace with short muffle 
for cupeling; others by the Hoskins’ gasoline furnace. 
They are all practicable, and the kind to use depends upon 
the amount of work to be done by it. 

27. For small work, where only a few assays are to be 








CRUCir.LE ASSAY FOR 


92 

made in a day, the Hoskin’s gasoline furnace is the best 
and cleanest: '^”t of the way places, the open char¬ 

coal furnace has to be resorted to; but coke is always pref¬ 
erable if it is to be had, and the furnace described in part 
first, page —, the best. 

28. Place your crucibles in furnace in unvarying order 
so that any given one may c ccupy the same place accord¬ 
ing to its number, and it is always a good plan to mark 
them with red chalk. If any of the assays fail, note the 
numbers, and make them again after all the others are 
done. For certainty, celerity and convenience, system is 
indispensable. 

29. In using the Hoskin’s gasoline furnaces, covers for 
the crucibles are unnecessary, and are seldom needed in 
any furnace except to keep the coals out of the pot; besides, 
the fusing mass may come in contact with the covers, which 
would render the assay unreliable. 

30. When the fusion is finished in from ten to twenty 
minutes, rinsed by a swinging movement, and tapped on 
the molding plate to settle the lead, and the liquid contents 
poured into a mold, the pot should be completely inverted 
and tapped against the mold. If the pot is free from ad¬ 
hering lead, and the nails (if they are used) also free from 
lead, the assay is finished. If lead is shown in globules in 
either the nails or pot, return the whole mass to the cru¬ 
cible and heat it again, and if the slag is thick or pasty add 
some borax or carbonate of soda to thin it, and submit it to 
a strong heat until it is perfectly fluid before pouring. 

31. When cooled the assay is turn'^d out of the mold, 
the button is then beaten out of the slag, hammered into a 
cube, brushed, marked, and placed in readiness for the cu¬ 
pel. The button must be soft and malleable and easily 
separated from the slag. 

32. The old style three-cornered Hessian crucibles are 


6 . 

7 - 


GOLD AND SILVER 93 

best in all cases, if they can be had cheap, for the reason 
that they cannot be used the second time. The assay is 
never poured, but cooled in the crucible, the crucible 
broken, and the button extracted, hammered to a cube, and 
treated as before stated. 

EXERCISES. 

1. \Vhat is the purpose of a preliminary assay? 

2. How does the experienced workman dress the 
charge? 

3. What is the first thing to consider in making a pre¬ 
liminary assay? 

4. If it is a reducer, what is added? 

How is the amount of flour to be added determined? 
What is one part of nitre equal to? 

What formula does Mitchell give for all gold and 

silver ore? 

8. What office does litharge perform as a flux. 

Wdiat amount of litharge is generally used? 

I 

What is the nail assay? 

What formula is used for ores containing quartz, 
clay, lime, or iron oxide? 

12. How is the soda and borax prepared for use? 

13. How do you determine the amount of soda or borax 
to be added? 

14. If the button is too large, how do you proceed? 

15. How do you adjust the proportions of litharge? 

16. How many parts of litharge would an ore contain¬ 
ing ten per cent of iron pyrites require? 

17. How does litharge affect copper? 

How should nitre be added? 

How may charcoal be added? 

What is added to the filtrate and washing? 

Why cannot salt be added during the treatment of 


9 - 

10. 

11. 


18. 

19 - 

20. 

21. 


the ore? 


94 


CRUCIBLE ASSAY 

22. How are the filters reduced to ash? 

23. What is the advantage in making assays in this 
way? 

24. What dressing is given by Mitchell for concentrat¬ 
ed pyrites? 

25. What dressing is used when the universal flux can¬ 
not be obtained? 

26. What is the most important thing for the student to 
learn ? 

27. What furnace is best for small work? 

28. What is said in regard to placing the crucibles? 

29. When are covers necessary? 

30. After the fusion is finished, how do you proceed? 

31. How is the button finished? 

32. What kind of crucibles are to be preferred, and what 
is their special advantage? 


CHAPTER TV. 


Scorification. 

1. This method of assaying the litharge required for the 
fluxing of the ore is made from lead during the operation. 
Scorification is well adapted for rich ores, but not for poor 
ones on account of the smallness of the quantity used. 
Ores containing nickel or tin are best scorified, even if made 
in the crucible; it cannot be cupelled until scorified. 

2. Granulated lead, like litharge, contains a small 
amount of silver; to determine the amount, take 

Granulated lead, 2 to 4 A. T. 

A little powdered glass. 

Mix in a scorifier; place in a heated muffle and close the 
door, maintaining a good heat; then open the door and 
keep a good red heat. Keep the lead fused, and when it is 
covered by the slag remove from the furnace and pour into 
a mold. 

3. Return the scorifier to the muffle and as soon as the 
assay is cooled enough to separate the slag, return the lead 
to the scorifier, and do tnis several times until a button of 
proper size is obtained for cupelling; when cupelled, note 
the weight of the lead, and of the amount used. 

4. In assaying the ore a small amount of borax glass is 
useful in fluxing, unless the gangue is quartz. With an un¬ 
familiar ore it is best to make several assays with different 
quantities of lead. The following is a general formula for 
ordinary ores: 

Ore. I part. 

Lead . 10 parts. 

Add a little dried borax unless the gangue is quartz. Mix 
one-half the lead with the ore and borax in the scorifier; 
cover with the remaining lead; place in a led-hot muffle. 
Close the door until the lead is thoroughly melted; open 




SCORIFICATION 


96 

the door and regulate the heat. The ore will be seen float¬ 
ing on the lead. It soon takes the form of a ring, leaving 
the lead exposed; this is called the.“Buirs Eye.” 

5. If the “Bull’s Eye” does not appear, the assay H a 
failure, unless it is an oxidizing ore. When the “Bull’s 
Eye” appears, keep it at a cupelling heat, which can be 
managed by opening or closing the door; add a little more 
borax if the “Bull’s Eye” is covered by the melted slag. 
When it is perfectly fluid the assay may be poured; if the 
button is too large, rescorify it to the proper size; then clean 
and cupel it. 

6. If the ore is a sulphuret, omit the borax until the 
“Bull’s Eye” appears; then it may be added. Some claim 
scorification as the best method, but it can only be so main¬ 
tained in rich silver ores. The crucible assay for gold is far 
superior, and more accurate by all odds. 

CUPELLING. 

The student must have practical experience in cupelling 
in order to thoroughly understand the operation. 

7. By this process the lead is separated from the metal. 
The cupel should be much heavier than the lead button; 
it is placed in the red-hot muffle with the cupel tongs and 
the door closed. When the cupel is thoroughly heated the 
button is placed in it and the door closed until the lead is 
well melted, when it is opened to give it air. When the 
lead appears luminous, the heat must be regulated by 
means of the ash-pit door, so that the lead smoke may rise 
to the middle of the muffle. The button gradually becomes 
smaller and colored spots appear on the surface. 

8. These spots are litharge, which sink into the cupel. 
After a time the heat may be reduced, not so much to chill 
the button, but just enough to show the crop of small crys¬ 
tals of litharge which form on the cupel. 


SCORIFICATION 


97 

9. In a short time the button will round up with thin 
scum on its surface and as it passes off the rainbow-colored 
rings will be seen to move rapidly and pass off. When this 
point is reached, the cupel is pushed further back into the 
muffle, where the heat is greater. Let it remain for a mo¬ 
ment. 

10. Suddenly the bead becomes still; in a few seconds 
the cupelling is finished, and when the cupel is drawn near 
the mouth of the muffle, the bead brightens or blinks. If 
the bead is mostly gold it is known by its greenish color 
while fused. The cupel may now be removed from the 
muffle, cooled and the bead weighed. 

11. If the bead is silver, it must be cooled very grad¬ 
ually; if cooled suddenly on the surface, while the cupel is 
hot, the gas when expelled from the interior, breaks 
through the solid crust carrying with it some molten silver 
which will fly off and be lost. This is called vegetating or 
sprouting. 

12. This can be prevented by cooling the bead very 
slowly, by pushing the cupel back and forth and tapping it 
on the sides with the tongs. 

13. If the button does not brighten, but cools or chills 
quickly, it probably contains copper, when more lead must 
be added, and again cupelled; this leaves a bright and clean 
button of gold or silver, or nothing at all, as is often the 
case. One of the most important things in cupelling a 
number of assays at one time, is to keep your cupels from 
getting mixed or changed. 

14. Each cupel should be numbered to correspond with 
the assay. Some assayers never mark their cupels, but 
trust to their memory,, or ihe location of the cupel in the 
muffle. I think it a bad practice, for the memory is very 
faulty, especially in removing cupels from the muffle. 
When one is finished and taken from the muffle, another 


) ) > 


98 SCORIFICATION 

may take its place: this often accounts for many false re- 
turns in an ore assayed. 

A mistake of this kind might give a good return for a 
man’s ore that had nothing in it, and a poor return for an 
ore that was really rich. 

15. I always mark my cupels on the side with an old 
case knife to correspond w ith the number and owner of the 
assay on my record book, and each number when cupelled 
takes its allotted place on the tray. 

16. Another point in cupelling silver buttons is to guard 
against excessive heat, b’ever go away and leave your as¬ 
says in the muffle to take care of themselves. Silver but¬ 
tons, when uncovered in c. strong heat will sublimate. In 
such a case your silver may be found clinging to the roof 
of the muffle. Watch the assays carefully from beginning 
to end. 

Practice makes perfect. Let the student take some proof 
silver, wrap it up in lead, cupr it, and note the loss, until 
he finds out what he can do. 

17. On removing the cupels from the muffle, place them 
on a tray in their regular order, and carry to the anvil. 
The large beads are seized by the plyers, laid on the anvil, 
and after being cleansed with a stiff brush are flattened 
with a small smooth hammer. Each bead as it is cleansed 
is placed on a watch gk ss bearing the set, and number of 
assay placed on the disk of paper pasted to the convex side 
so that it can be read through the glass. 

18. The glasses are arranged on a tray similar to the 
cupel trays. 

Some assayers have a bad practice of placing the bead 
back on the cupel from which it came and carrying them 
to the scales in that rr'anner. It leads to occasional loss. 
Sometimes the bead is carried some distance in the plyers 
to be weighed, and is liable to be dropped on the floor, 




WEIGHING THE BEAD 


99 

where a very small bead could not be found. The tray with 
the watch glass containing the bead on it can*be placed 
close to the scale pan of the balance, where the loss of the 
bead is almost impossible, and without dirt, as is the case 
with the cupel. 

19. The weight of the bead is noted in a book kept for 
the purpose, opposite to the set and sample number; under 
the weight is noted the correction due to silver in the 
litharge or lead used in the assay, which being subtracted 
leaves the net weight of the precious metal obtained from 
the ore. There is always some silver lost in the cupelling, 
but it is not worth while to make a correction for it, ex¬ 
cept in a bullion assay. 

WEIGHING THE BEAD. 

20. Again I must call the attention of the student to 
this most delicate instrument, the balance. By it alone the 
result of an assay is determined, and too much care cannot 
be taken in weighing the bead and adjusting the balance. 

21. Eirst see that your balance is properly adjusted and 
that no dust is on or about the beam. If so use a camel’s 
hair brush to clean it. 

Place the bead on the left-hand pan, because the right 
hand is then conveniently employed in adjusting the 
weights on the right-hand pan, while the left operates the 
turnkey by which the supports are raised or lowered. 

22. When equilibrium is nearly attained, the case must 
be closed, because the slightest current of air, or even your 
breath will disturb the action of the balance. It is here that 
the great convenience of the riders and carriers are realized. 
The weights having been adjusted to the ten or there¬ 
abouts, the case is closed and the operation finished with 
the rider, by moving it to the right or left until perfect 
equilibrium is attained. 

23. When riders are not used, the fractions of a unit 


) 

> > 
) ) ) 


) 




lOO 


WEIGH TNG THE BEAD 


may l)e estimated by the oscillations of the pointer. Many 
new be^'ii’iners suppose the ivory scale indicates i-io of the 
units of weip;ht of g'rains or grammes, but it is not so. 

24. The divisions are only intended to mark the range, 
swing, and rest. Range is the total movement of the index, 
counted in divisions of the arc (called vernier by some), 
and may extend to each side of zero; again the pointer may 

move to either side and not return to zero. It has no value 
as an indication of the amount of preponderance, but from 
it we calcida.te swing and rest. 

Swing is the excess of movement to one side or the other 
of zeio, caused hv the preponderance of weight in one of 
the pans; hence the balance in e(|uilib’'ium will have range. 

Swing is ecual to range when one extreme of range is 
zero: it is the difference of the distances from zero when 

the pointer goes to each side of zero, that is, when the 
signs of the distances are opposite: it is the sum of the 
distances when the signs are similar. 

25. Range is a matter of observation only. It may 
be increased whenever desired by a waft of the hand, a 
slight current of air against either of the hands, after which 
the case mav b-e closed, and after a few moments begin the 
observation. 

“ Range (an average) is 8)< —3, as the signs 
are opposite, swing is the difference, = XS- rest is 
X2T Again: range is —8X3: the signs are opposite and 
the swing is —5: rest, 2^. 

‘‘Weighing by oscillation is useful only when riders are 
not in use. It avoids handling the lesser weights and fin¬ 
ishes with the case closed. 

“If you can understand the foregoing method of obtain¬ 
ing the true swing, arrange your balance so that if not in 
perfect equililnium, any swing it may have shall be to the 
right: then iii each weighing subtract the previous from the 
present swing. The remainder will be the true swing. 



PARTING THE BEAD 


lOI 


“I have heard some learned talk from beginners about 
weighing down as low as three cents per ton in gold, when 
in fact $10.00 per ton would be nearer the truth. 

26. “It will take an hour to adjust the best balance made 
to weigh as close as 15c per ton. it is no funny job. It 
can only be done by the method I have here pointed out— 
by range, swing, and rest. If a man is going to be an as- 
sayer, he must learn the business, and not learn just enough 
to expose his ignorance of it.”—C. H. Aaron. 

PARTING THE BEAD. 

27. Beads obtained from ore always contain more or 
less silver, and are parted by boiling in nitric acid. In 
order to separate them completely, it is necessary that the 
alloy shall contain at least twice as much silver as gold, and 
that it be flattened to a thin sheet unless it has as much as 
three parts of silver to one of gold. In a large proportion 
of silver the gold is left in the form of dark powder. Beads 
obtained from an ore frequently contain sufficient silver for 
a successful parting. In small beads it is a good plan to 
add a known weight of pure silver to collect the gold and 
keep it from sinking into the cupel. 

28. When the bead is yellow and gold predominates it 
requires the addition of two to two and one-half parts of 
silver'. 

If, on attempting to part the bead, it is found to be 
blackened, but not much affected by the acid, it requires 
two parts of silver. 

29. This addition of silver is called inquartation. For 
this purpose some test silver cut into small pieces is kept 
on hand in a small box in the scale drawer. 

30. For small beads the silver need not be weighed, but 
select a few pieces which are known to be sufficient, it 
matters not if it is four times as much as the gold. 


102 


PARTING THE BEAD 


The silver and bead may be folded in a small piece of 
thin sheet lead and cupelled, the bead cleaned as before, 
flattened on the anvil, parted, washed, and ‘Tupped,’^ 
heated to redness, and weighed. The acid for parting need 
not be strong; 32 Baume is sufficient, and will be less 
liable to lumping or breaking up the gold than stronger 
acid. 

31. The test tube is best for parting. Heat it with a 
spirit lamp or gas flame gently. When the parting is com¬ 
pleted, and the gold has collected together, the acid is 
poured off. The tube is then filled with pure water and the 
gold allowed to settle, when the water is poured off. The 
tube is again filled with water and held between the fingers 
of the right hand. A dry cup is inverted over it and re¬ 
tained by the thumb. By turning the wrist the tube is in¬ 
verted and the gold settles through the water to the bot¬ 
tom of the dry cup which is now right side up, the mouth 
of the inverted tube within it. 

When the gold is settled the dry cup is held by the left 

hand, the tube by the right, and the latter is carefully raised, 

allowing air to enter and the water to escape, nearly filling 
but not overflowing the cup. ^ 

32. Allow the disturbed gold to settle; work the mouth 
of the tube up on the edge of the dry cup and scrape it off 

quickly, not allowing any of the water to enter the dry cup 
to throw the gold out. ^ 

The cup now contains the water and the gold; tap it to 
collect all the gold in one body; then draw the water off 
with the aid of a glass rod, draining it as much as possible- 
then take it to the muffle on the tray and place therein with 
the tongs; heat it to a redness; again place on the tray, and 
when cooled, carry it to the balance for weighing in its retr- 


CALCULATING THE ASSAY 


103 

The weight of the gold noted, from the weight of the 
bead from which it is substracted, leaves the net weight of 
the silver. 

33. 'Frequently the gold ores from one mine where the 
fineness of the bullion is well known and the value per 
ounce determined, the bead may not be parted, but the 
value per ounce be calculated according to its known value, 
say at $16.00 or $17.00 per ounce, or whatever it may be; 
this saves much time and labor in parting the beads. 

CALCULATING THE ASSAY. 

34. On weighing, the gold and silver from an assay are 
always reported, as before stated, in units and decimal 
fractions of the units of the system of weights used. 

As a ton of 2,000 pounds of ore contains fourteen million 
grains, it is easy to calculate by proportion, that if one. 
ounce troy (480 grains) contains i-ioo of a grain a ton 
would contain .6060 ounces, which, if gold, would be worth 
$12.40: if silver, 77c or $1.29 per ounce. 

35. These figures are, therefore, constant factors, and 
multiplying the weight of metal obtained from such an as¬ 
say in units of the system by these factors gives us the 
ounces in a ton, or the value in dollars and cents. 

36. The best method is to take such a weight of ore as 
contains as many points or units of the assay set as there 
are troy ounces in a ton of 2,000 pounds, that is, 29.1666X 
such a weight, is called the assay ton, and the sign for it is 

A, T. 

In the grain system, that is when the bead is weighed in 
hundredths of a grain and fractions thereof, the ton con¬ 
sists of 291.67 grains and each point of bead weight, gold 
or silver, corresponds to one ounce of the metal in a real 
ton of the ore. 

37. In the gramme system, where a point is a milli- 


104 CALCULATING THE ASSAY 

gramme, the ton consists of 29.167 grammes, and, as in the 
other case, each point of bead weight corresponds to one 
ounce in the real ton of the ore. This, of course, can be 
halved or quartered to suit. 

38. An ounce of gold is calcinated as worth $20.67 
ounce, and an ounce of silver is calculated at $1.2929, but 
this is only the assay value of silver ; at present it is worth 
less, and the value thus found must be discounted accord¬ 
ing to the market value; but it is best to report the silver 
in ounces per ton alone. 

EXERCISES. 

1. To what kind of ore is scorification particularly 
adapted? 

2. How would you make a charge of granulated lead 
to determine the amount of silver it contained? 

3. If the lead button was too large to cupel how would 
you treat it? 

4. How would you make the dressing of an ore assay, 
and what would you add? Would you add borax if the 
gangue was quartz? 

5. Suppose the '‘BuH’s Eye” did not appear, what 
would you do? 

6. In what kind of ore might the borax be omitted? 

7. What is the philosophy of cupellation, and why 
should the cupel be heavier than the lead button? 

8. When spots appear on the surface of the button, 
what does it indicate? 

9. When the button rounds up at the close of the cu¬ 
pellation what is indicated? 

10. How does the bead act near the close of the cupel¬ 
ling? 

11. How would you cool a bead that was all silver? 

12. How can the Vegetating be prevented? 


CALCULATING THE ASSAY 105 

13. What is indicated by the non-brightening of the 
button? What would you do? 

14. How would you prevent the cuples getting mixed, 
or the numbers changed in the muffles? 

15. How would you mark your cuples? 

16. Do you need a high heat in cupelling? 

17. In removing the cupels from the muffle, how would 
you treat the beads? 

18. What are the watch glasses used for? 

19. How is the note-book used? 

20. What is the most important instrument in the as- 
sayer’s office? 

21. What is the first duty in weighing the bead? 

22. Describe the process of weighing the bead. 

23. Of what benefit are the riders, and when are they 
used? 

24. What do divisions on the Ivory scale denote, and 
for what are they used? 

25. Describe the range, spring, and rest. 

26. How close can gold be weighed, and caalculated in 
dollars and cents? 

27. Is gold found pure or as an alloy, and how would 
you put it? 

28. If, on attempting to part the bead, it burns black, 
what is indicated, and how would you proceed? 

29. What is the addition of silver called? 

30. How is silver added to small beads? 

31. What is used to part the beads? 

32. Describe the process of parting in full. 

33. When may the parting of the bead be dispensed 
with ? 

34. How would you report an assay of one ounce of ore 
in one one-hundredth of a grain? 


io6 CYANIDE PROCESS 

35. What is the constant factor for one ounce, and for 
one-half ounce? 

36. What is the best system to use? 

37. When A. T. is used, what does one point indicate? 

38. What is gold valued at per ounce, and what silver? 

LABORATORY TEST OF EXTRACTING GOLD BY 
THE CYANIDE OF POTASH SOLUTION. 

The precipitation of gold from cyanide solution by zinc 
shavings has been more generally used than any other pro¬ 
cess. It appears on the face of it to be the simplest method 
that could be devised when properly done, and gives better 
results than any other in use. Yet many who have de¬ 
scribed the application of the cyanide process have not 
given sufficient weight to the complete precipitation of the 
gold from the solution. It is not so simple a matter as some 
are led to believe,to completely precipitate all the gold from 
the potassium-aurocyanide solution. 

1. Although the action of zinc on gold solution is a very 
simple substitution of gold from the the zinc in accordance 
to the following equation: 

2. 2 Au, K, Cy2 -|- Zn = K2 Cy^ -|-2Au 

Its completeness seems to depend entirely upon a slight ex¬ 
cess of cyanide of potassium being in the solution. 

3. It must be remembered that no ores containing zinc 
of any kind, can be treated by this method. 

4. Therefore it is always best to test all ores for that 
metal before submitting it to the cyanide solution, especi¬ 
ally if the ore is a sulphuret. 

5. Take one pound avoirdupois—or any number of 
pounds—of the fine pulverized ore and place it in a heavy, 
wide-mouthed glass jar. 

6. Weigh out seventy grains of the commercial cyanide 
of potash to each pound of the ore used; dissolve it in water 
of an eciual weight of the ore, pound for pound, and pour 


CYANIDE PROCESS 107 

it into the ^lass jar with the ore; shake it until the ore is 
saturated; cork it and set it aside for two days, occasionally 
agitating by shaking. 

7. If the gold in the ore is very coarse allow it to stand 
a week before leaching it out, as it takes time to disolve 
coarse gold. 

8. When sufficient time has elapsed to dissolve the gold 
prepare a large funnel, fitted with a coarse filter, and in the 
bottom place a half-ounce or more of fine zinc shavings; 
on this fit another coarse filter paper, upon which decant 
the aurocyanide solution, and let it percolate through the 
zinc shavings into a vessel; add a little water, wash the pulp 
and again decant on the filter. Do this several times until 
the pulp is well leached. 

9. Then take off the second filter with the sediment and 
pour the aurocyanide solution over the zinc shavings five 
times; it will percolate through the shavings, and the gold 
and silver will be found to have replaced the zinc to the full 
extent of the metal which was in the ore. 

10. Now plug up the outlet of the funnel, and pour over 
the zinc shavings a weak solution of sulphuric acid which 
will dissolve the zinc, leaving the gold on the filter; remove 
the filter from the funnel, cut off all not containing the 
gold, dry, and burn the filter to an ash; envelope the gold 
and filter-ash in a sheet of lead and cupel; weigh the gold 
obtained, and calculate the value per ton from the amount 
of ore used. 

11. If doubts exist as to whether all the gold is extract¬ 
ed from the solution, add a little chloride of zinc to the 
leached solution; let settle; decant and filter, and make an 
assay of the residue. 

In order to test the above reaction, I make up a solution 
of potassium aurocyanide with about one per cent of metal¬ 
lic gold and no free cyanide. A solution was made from 


io8 


CYANIDE PROCESS 


this so as to contain o.i per cent, or about $600.00 per ton, 
gold. I treated this with a piece of clean, bright zinc 
(common commercial zinc), which is always used in prac¬ 
tice. This was immersed and agitated in the solution for 45 
hours, when it was taken out and carefully weighed; but 
not a trace of gold, to the amount of a hundredth part of a 
miligram, could be detected, and after dissolving it in 
weak sulphuric acid, there was still not a trace of gold to 

be found. This made me think the gold could be extracted 

« 

from the ore, but not from the solution. Any one trusting 
to this would naturally throw it away, when at the same 
time it contained $600.00 per ton. I next prepared some 
zinc shaving by scraping it with a sharp knife, and placed 
it upon a filter paper in a funnel, then placed a second filter 
over the zinc shavings, so the solution would slowly perco¬ 
late through the zinc, and, after decanting the solution 
through these shavings five times, was able to collect the 
whole of the gold on the zinc, where it seemed to replace 
the zinc, for, when the zinc was completely dissolved in 
weak sulphuric acid, I found the gold in the same form as 
the zinc shavings were themselves. This was all done in 
24 hours. It was a mystery to me why the gold should 
precipitate on the zinc shavings, and not on the bright zinc 
plate. 

The indications point to polarization, so well known in 
electrolytic work. But whether, on the bright zinc plate, 
the invisible trace of films put a stop to further action by 
preventing contact or producing an opposite electric force, 
is a question. 

1 here is no doubt of the tendency of potassium-aurocy- 
anide to split up into K. Cy. and Au. and C., which is as¬ 
sumed in the reaction by substitution. Then, again, there 
is a tendency to split up along another line, viz., K. and 
Au. Cy., like an acid reaction. Now, if this be the case 


ASSAY OF TIN ORE 109 

in the presence of zinc and water, the water will be attacked 
by the potassium and 'he An. Cy.2 will be attacked by the 
zinc, forming zinc cyanide and metallic gold. It can only 
take place by the condition of the polarization on the sur¬ 
face of the zinc, owing to the film of hydrogen set free on 
its surface; if this is so, it is very clear why the zinc shav¬ 
ings will act when the polished zinc plate does not, the zinc 
shavings having a larger number of ragged edges, which 
causes the escape of the hydrogen gas and allows the reac¬ 
tion to go on. When the reaction once sets in, there is a 
further reaction between the caustic potash and the zinc 
cyanide, which dissolves a part of the latter. The main 
point would be: Is hydrogen fonned on the surface of the 
zinc plate, or is it absent? It is well known that when the 
zinc is forming on zinc shavings hydrogen gas is set free. 
It does not form at first, but upon shaking the zinc shav¬ 
ings fine bubbles of gas escape and can be easily collected, 

ASSAY OF TIN ORE. ^ ' ■ ’ 

There are many methods of conducting the fire assay of 
tin ores, but none excel a cyanide flux as a reducer, al¬ 
though for many ores carbonate of soda and borax will do 
as well, 

1. Take 200 grains or twenty grammes, or any other 
convenient quantity of finely pulverized ore (and it is al¬ 
ways advisable to make two independent parallel assays 
with the view of having a control), and take the highest re¬ 
sult obtained upon which to place reliance, since the error, 
if any, must be oh the side of the loss, rather than the ex¬ 
cess. 

2. Take the old Hessian crucible if at hand, or any clay 
crucible will do. In the first place ram into the bottom of it 
a small charge of powdered cyanide of potassium sufficient 
to form a layer of about a half inch in depth. 


no 


ASSAY OF TIN ORE 

3. The weighed quantity of tin ore is then intimately 
mixed with four or five times its weight of powdered cyan¬ 
ide, and the mortar rinsed with a small quantity of the flux 
which is laid on top of the mixture. 

4. The crucible is then heated in a moderate fire for ten 
minutes with a steady fusion heat so that it will not boil 
over, until it flows smoothly; cool; break the crucible, and 
extract the button of tin which will be silvery white; weigh 
and calculate the percentage of tin. 

5. Assay of Tin Ores Which Contain Arsenic, Sulphur, 
Tungsten (Wolfram).—In all such ores it is necessary to re¬ 
move them before attempting to obtain the tin in a pure 
state, by fire assay. 

6. The l^est method of treating all such ores is to de¬ 
compose them by nitro-hydrochloric acid (aqua regia) at 
the boiling temperature. The oxide of tin alone is not af¬ 
fected by it. 

7. Take 400 grains or more of the impure tin ore pul¬ 
verized; place it HI a boiling flask, and add one-half ounce 
of hydrochloric acid and one-half ounce of nitric acid. 
Heat gently for half an hour, then boil until the greater 
part of the mixed acids are evaporated. 

8. This will cement the sulphur and arsenic into sul¬ 
phuric and arsenic acid. The iron and manganese will be¬ 
come soluble. 

9. The tungstaic acid will remain in the insoluble state 
with the oxide of tin and silica. 

10. Allow the flask and contents to cool; add water and 
let settle, and decant. Continue doing so until the water 
passes off tasteless. 

11. The insoluble matter in the flask is now oxide of 
tin, silica and tungstaic acid. 

12. To remove the latter digest for one hour at a very 
gentle heat with one ounce of solution of caustic ammonia 


ASSAY OF TIN ORE 


III 


with occasional agitation; add water and van the remain¬ 
der to separate silica. Nothing now remins but the oxide 
of tin, with a little silica. This is dried and assayed as first 
stated with cyanide of potassium. 

13. Oxide of tin alone, the protoxide, in the state of 
hydrate, lights and burns like tinder and becomes peroxi- 
dized. 

14. Wolfram is a tungstate of iron and maganese (Fe 
Mn) W. 0.4 in which the proportion of the two metals is 
variable, and generally associated with tin ores. 

15. To determine the tungstate, the finely powdered 
mineral is heated with acqua regia until it is completely de¬ 
composed. The solution is evaporated to complete dryness 
over a water bath, water added, and the manganese and 
ferric chloride filtered off. 

The residual tungstic acid is washed with alcohol, dis¬ 
solved in ammonia, the solution filtered from any residue, 
evaporated to dryness in a capacious porcelain crucible, 
gently heated to expel ammonia and ignited by contact 
with the air. 

16. The tungstic oxide is then weighed; it should have 
a pure yellow color free from any greenish tint. 

Til ere are several methods of determining the amount of 
tin and tungsten in an ore by volumetric analysis, but for 
all practical purposes the above is sufficient. 

EXERCISES. . 

1. What is the philosophy or reaction of gold on zinc 
in a cyanide solution? 

2. State the equation. 

3. What depends upon saving the gold? 

4. For what purpose would you test all ores before 
treating them with cyanide? 

5., State the amount and arrangement of ore used for a 
charge. 



112 ASSAY OF TIN ORE 

6. What strength of cyanide is used, and how is it pre¬ 
pared ? 

7. How is coarse gold treated? 

8. What is the method of treating it? 

9. How many times is the zinc treated with the auro- 
cyanide solution? 

10. How is the zinc separated from the gold? 

11. When doubts exist as to whether all the gold has 
been taken from the solution, how is the fact determined? 

EXERCISES. 

1. How much ore would you take for a tin assay, and 
how would you control it? 

2. What would you use for a flux? 

3. How would you arrange the charge in a crucible? 

4. How would you arrange the heat at first? 

5. What are the principal constituents of a base tin 
ore? 

6. What is the best method of treating a base ore of 
tin? 

7. What acids are used, and how much of them? 

8. What are tlie acids converted into? 

9. How, and in what form is the tungstate left? 

10. At what point would you decant and wash the con¬ 
tents of the filter? 

11. Of what is the residue on the filter composed? 

12. How is it removed and treated? 

13. How many oxides of tin are there, and how con¬ 
verted one to the other? 

14. What is the wolfram? Give the formula. 

15. What ores is it associated with, and how is it de¬ 
termined? 

16. What is the appearance of the tungstic acid, and 
what is it called v/hen dried and weighed? 


COPPER ASSAY 
COPPER ASSAY. 


113 


1. The fire assay of copper is never perfectly accurate, 
although many kinds of copper ores can be assayed within 
one per cent of the truth by it, and it will always do for a 
prospect assay, if above fifteen per cent in copper. 

2. Poor ores and all which contain lime or baryta and 
sulphur had best be submitted to a matte smelting, which 
gives a richer product to work on, and in the second place 
it removes calcium or barium sulphate, which causes a 
loss. 

3. Ores containing less than eight per cent of copper, 
C. H. Aaron recommends the following charge: 

Ore . 400 grains. 

Borax glass. 400 grains. 

Flour . 20 grains. 

Sulphur . 10 grains. 

Mix in a wedgewood mortar; put in a pot and cover with 
salt; over that again put 400 grains of borax glass. If 
there is any sulphur in the ore omit the flour. 

4. If there is any lead in the ore add three nails. Melt 
slowly and finish with a strong heat; when melted let it 
cool in the crucible; separate the matte from the slag, and 
from the lead if any, and reserve it for further use. 

5. Ores which are rich and combine with baryta, lime, 
gypsum, heavy spar, or sulphurets of any kind is best con¬ 
verted into a matte by the following charge: 

Ore ... I part. 

Borax.. i part. 

6. Add sulphur if there is none in the ore; place in the 
crucible; cover with salt and borax, and add nails if lead 
be present; melt down, cool, and reserve the matte for the 
determination of copper. 









COPPER ASSAY 


114 

RICH SULPHURETS OF COPPER WITHOUT 
LEAD, LIME OR BARYTA. 

7. These include the mattes from the preceding as well 
as the natural ores. Pulverize the ore, roast it in a roasting 
dish with a little charcoal, beginning with a low heat and 
raising it gradually to a bright redness, stirring with an 
iron wire occasionally. 

8. When no more odor is perceptible from the red-hot 
ore, cool and grind again. 

9. Take notice if any arsenic is present or not; if so it 
has an odor like that of garlic. 

If arsenic is present add a little more charcoal; re-grind 
and continue the roasting until expelled. 

10. Then place on the ore a little carbonate of ammonia, 
mix it with the ore and heat; it will remove the last traces 
of sulphur. The ore is now in the following class of 

RICH OXIDIZED ORES. 

11. The ore may be a natural oxide; if so it must be 
weighed and calcined by heating to redness in a roasting 
dish; mix in crucible the following charge: 

Ore . I part. 

Soda . 2 parts. 

Argol . I part. 

Lime. | part. 

In place of soda, cyanide of potash may be used with 
good advantage. If much quartz is in the ore add a little 
powdered iron ore;mix well in wedg wood mortar. Place 
in crucible which should be more than two-thirds full; cover 
with salt and borax glass. 

12. Heat very slowly at first to a dull redness for 10 
minutes, then give it a high heat; remove from the fire 
qpickly, wash the pot with the slag, tap to settle all glob¬ 
ules; cool and break the pot. The copper will b^ found in 
a single button. 






COPPER ASSAY 


13. If the button is malleable and of a good color, it may 
be weighed and the percentage calculated. But if the but¬ 
ton is black or gray it must be refined by cupellation. 

REFINING OF PURE COPPER BUTTON. 

14. Place the button in a highly-heated cupel with an 
equal weight of pure copper on another. Add to each one- 
tenth part of lead and close the mufile door. 

When the buttons are well melted, open the door to ad¬ 
mit air, and the refining begins. 

15. The heat must be higher than for a silver assay, and 
the final brightening is much less vivid. The moment the 
lead leaves the copper it solidifies. Continue this operation 
by adding the one-tenth lead and cupelling until the copper 
is purified; cool by placing the cupel and button in cold 
water. Clean and weigh the buttons, and to the assay but¬ 
ton add as much as the pure button has lost, and calculate 
the percentage. 

16. If gold and silver is suspected to be in the ore, add 
lead and continue cupelling until all the copper is com¬ 
pletely cupelled off. Then weigh the resulting bead. 

VOLUMETRIC METHODS. 

17. There are many methods of determining copper 
volumetrically, that is, by the volume of a re-agent which is 
found to be necessary to produce or complete a certain 
effect in the suitably prepared solution; the best in my 
opinion, and the one most commonly used, depends on the 
fact that the blue ammoniacal solution of copper is dis¬ 
colored by a solution of potassium cyanide that is generally 
known as the 

CYANHDE PROCESS. 

18. * Take one gramme of pure copper, dissolve it in 
nitric acid: add ammonia until the p.p. at first formed is re- 


COPPER ASSAY 


ii 6 , 

dissolved to a blue liquid ; and then filter off the precipitate 
of iron; add water to make about 200 c.c. in a boiling flask. 
Charge a Mohr burette with a solution of potassium cyan¬ 
ide made by dissolving one troy ounce in five and a half 
fluid ounces of water, and filtered if necessary. 

19. Run the liquid from the burette into the blue solu¬ 
tion of copper, stirring it with a glass rod, until the blue 
color becomes faint and purplish; continue cautiously add¬ 
ing the cyanide, little by little, finally drop by drop, with in¬ 
tervals between until only a faint tint remains which disap¬ 
pears in a few minutes, leaving the liquid colorless; observe 
how many c.c. of the cyanide has been used by the mark on 
the burette, and note the number. 

The cyanide solution is thus titrated; that is, it is known 
what volume of it corresponds to one gramme of copper in 
the assay. This is called the standard cyanide solution and 
should be kept in a dark-colored bottle, stoppered. 

20. To make the assay of the ore, take one or two 
grammes, more or less according to the richness of the ore, 
and make an acid solution by one of the methods previ¬ 
ously described, or by nitric acid alone. (Some take pains 
to expel the nitric acid by addition of zinc or evaporation, 
but it is not necessary). Add ammonia in excess, and heat 
to boiling for some time; filter off the iron, silica, etc., and 
wash with water until it passes through colorless. 

21. The entire volume of the solution, including the 
washings, should not be more than 200 c.c. 

When quite cold add solution of potassium cyanide from 
the burette precisely as in titrating the standard solution, 
noting the quantity used. 

22. To determine the assay is now only a matter of 
proportion or the “rule of three.” For instance, if one 
gramme of pure copper reciuired 80 c.c. of cyanide solution 
to clarify it, and one gramme of the ore required 30 c.c., 


COPPER ASSAY 


117 


then 80:30:: 100:?. the copper in the assay =37.5 per cent. 

23. The interfering elements in this process are man¬ 
ganese, which can be obviated by adding a little carbonate 
of ammonia. 

Arsenic also interferes, but can be overcome by adding 
a little of the magnesia mixture. 

24. Nickel, cobalt, and zinc, are all fatal to the accuracy 
of the process. If they, or any of them are present, it is 
better to precipitate the copper by means of a platinum 
dish. . 

25. Pour the solution into a platinum dish of known 
weight, add a piece of pure zinc; the copper is precipitated 
on the dish, to which it adheres, making it easy to wash. 
The whole of the zinc is to be dissolved, acid being added 
if necessary, until no more bubbles are seen. 

26. The copper is w^ashed, dried and weighed on the 
dish. The weight of the dish deducted leaves the weight 
of the copper, which is removed from the dish by means of 
nitric acid, which does not attack the dish. 

EXERCISES. 

I. Is the fire assay of copper correct? 

• 2. How should poor copper ores containing sulphur, 
baryta, or lime be treated? 

3. What is Aaron’s method for ores less than 8 per 
cent in copper? 

4. Should nails be added? 

5. How would you treat rich ores containing lime, 
baryta, or gypsum? 

6. Would you add sulphur and nails to make a matte? 

7. How would you treat rich sulphurets of copper 
without lime or baryta? 

8! How would you know when all the sulphur was 
expelled from the ore under heat? 

9. \\1iat is the odor of arsenic? 


ii8 LEAD ASSAY 

10. Why add carbonate of ammonia to finish a roast? 

11. How would you make a fire assay of rich oxide 
ores? 

12. How would you arrange the heat? 

13. What are the indications of a good fire assay? 

14. How would you refine a copper button? 

15. What kind of a heat is required in refining a copper 
button? 

16. If gold and silver are suspected in the button how 
would you treat it? 

17. What process is mostly used in the volumetric sys¬ 
tem of copper assays? 

18. How would you prepare a standard solution of cy¬ 
anide of potassium? 

19. How would you titrate it? Explain it in full. 

20. How would you make the assay with it? Explain 
in full. 

21. What amount of solution is best for titration? 

22. How would you calculate it? Give an example. 

23. What are the interfering elements, and what are the 
remedies? 

24. When nickel, cobalt, or zinc is present in the ore, 
how would you treat the solution? 

25. Explain the process of precipitation and calculation 
of the assay in a platinum dish. 

26. How would you remove the copper from the plati¬ 
num dish? 

LEAD ASSAYS. 

I. Numerous methods have been proposed for the de¬ 
termination of lead, by the fire assay, gravimetric, and vol¬ 
umetric systems, but the fire assay is the one most exten¬ 
sively used in the United States and elsewhere for the de¬ 
termination of lead in purchasing ores. 


LEAD ASSAY 


119 

2. The advantages are the ease of execution and the 
large number of assays which can be made in a short time. 

3. The disadvantages are that all the lead is seldom re¬ 
duced, and the buttons are seldom pure, and may contain 
more or less antimony, tin, copper, bismuth, iron, or zinc, 
yet the fire assay is the only method which the western 
smelters will accept for r basis for the purchase of ores. 
H. Van F. Furman says the fire assay of lead ore is too 
high; Mr. C. H. Aaron says that it is too low. 

4. But beyond doubt, ihe graviriietric determination is 
the most accurate method of all, but it takes time, and very 
careful manipulation. 

5.. The fire assay is most generally practised in Colo¬ 
rado. For ordinary ores the crucible is used, taking one 
part of the ore with four parts of the lead or universal flux, 
mixed in a clay crucible and covered with borax, and fused 
in a muffle furnace. The time of the fusion with a good 
heat is from 15 to 20 minutes. In the case of sulphide or 
base ores two or three nails are used in the charge. When 
the fusion has become quiet the crucible is allowed to re¬ 
main in the muffle three or four minutes, when it is drawn 
out and poured into a mold. 

As soon as cold the button and the slag are removed 
from the mold, and the button extracted from the slag by 
pounding with the hammer. 

6. The button, which should be malleable and soft, is 
flattened on the anvil. If brittle, it contains copper, anti¬ 
mony or iron. The slag should be vitreous and brittle, and 
should contain no shots or globules of lead. Where great 
accuracy is required, it must be made in duplicates which 
must agree within one-half per cent. 

7. The best method I have found for the fire assay of 
lead ore, where the ore is a pure sulphide of lead, is to use 
no other flux than pure bicarbonate of soda, taking three 


120 


LEAD ASSAY 


parts of the soda to one of the ore and covering it with 
salt. Nails are not required and the button is always found 
malleable and clean. 

8. If the ore is oxidized or carbonized at all use a little 
argol (crude tartar) and cover with salt. 

The sulphur has a greater affinity for the soda than it 
has for the lead; therefore, under the action of heat it leaves 
the lead and combines '^dth the soda to form sulphate of 
sodia with the slag. 

9. To ores which contain copper oxide or carbonate, 
and not enough sulphur to combine with the copper so as 
to keep it in the slag, some sulphur may be added for that 
purpose, or the weighed assay may be boiled in nitric and 
sulphuric acid, which will dissolve the copper, leaving the 
lead as an insoluble sulphate; the liquid must be diluted 
with water and filtered off; the residue dried, dressed and 
smelted for the lead. 

10. A general formula for the dressing of lead ores is 

Ore . I part. 

Soda. 3 parts. 

Flour or argol . i-io part. 

Borax. J part (nearly). 

Mix in a crucible, add several nails and cover with salt. 

11. If the ore is a complex sulphuretted one, keep in 
the fire twenty minutes after frothing has ceased. 

Pure carbonate of lead (crucite) does not require nails, 
and can be melted and poured quickly. 

12. The lead button can be cupelled for precious metals 
like the gold and silver ore assays, and the value calcu¬ 
lated accordingly. 

There are several volumetric methods of determination 
of lead in ores by standard solution, but as so many 
methods might tend to confuse the student I shall confine 






LEAD ASSAY 121 

myself to one wet assay as recommended by C. H. Aaron, 
viz: 

13. “Take a weighed quantity of the powdered and 
dried ore with a mixture of nitric and sulphuric acids (a 
little hydrochloric acid may be added if necessary), in a 
covered casserole or porcelain dish. 

14. “Boil until the ore is decomposed and until dense 
white fumes of sulphuric acid are evolved while still some 
liquid remains (otherwise add some sulphuric acid). Cool; 
add water cautiously; digest warm for a short time; filter, 
and wash with water to which a few drops of sulphuric acid 
have been added. After draining, remove the filter, with 
its contents, from the funnel to a porcelain dish or beaker; 
unfold, and lay it flat on the bottom. 

15. “Cover it with ammonia and add acetic acid until 
the mixture distinctly reddens blue litmus paper. Keep 
warm for half an hour, stirring occasionally. Decant the 
liquid upon a filter; wash the residue in the dish several 
times by decantation. 

16. “Add to the water at first a little ammonium acetate 
made by mixing ammonia and acetic acid, with care that 
the acid predominates; finally transfer all, including the 
original filter, to the filter and complete the washing; the 
filtrate contains the lead in solution and may also contain 
lime, not baryta nor strontia. 

17. “To the filtrate add dilute sulphuric acid as long as 
it produces a p.p. Heat; settle; filter; wash with sulphuric 
acidulated water, finally, once or twice, with pure water, or, 
better, with alcohol. 

“The lead is now on the filter in the form of sulphate, as 
it was after the first filtration, but freed from impurities. 
Dry it on the filter; transfer it to a small porcelain crucible 
of known weight or counterpoise; burn the filter; add the 
ashes to the p.p. and moisten them with a drop of sulphuric 


122 


LEAD ASSAY 


acid; heat nearly to redness, cool and weigh in the crucible. 
If very particular, burn another filter of equal weight with 
the first, moisten the ashes with sulphuric acid, and put 
them on the weight pan when weighing; a convenient way 
in which to manage this is to let the counterpoise, or part 
of it, be another crucible in which the second filter may be 
burned and the ashes treated as described. 

18. “Unless for very particular work, the lead sulphate 
may be weighed on the (tared, etc.) filter, after drying at 
248 Fahr. (in the air-bath). The lead sulphate contains 
68.32 per cent of lead. 

19. “A modification of the process is as follows: Treat 

the ore with acids as above; wash thoroughly with sul¬ 
phuric acidulated water, so as to remove all lime; dry the 
insoluble matter, consisting of lead sulphate, silica, barium 
sulphate, etc., and weigh it; extract the lead sulphate by 
means of ammonium acetate as above; wash, dry and weigh 
the residue. The loss represents lead sulphate, and, multi¬ 
plied by .6832, gives the weight of the lead. As calcium 
sulphate is soluble in ammonium acetate, great care must 
be taken to insure its absence from the first-weighed resi¬ 
due by thorough washing.’’ , 

EXERCISES. 

1. What method of lead assay is mostly practised in 
the purchase of ores? 

2. Why is it especially advantageous? 

3. What are the disadvantages? 

4. Which is the most accurate of all? 

5. What method is mostly adopted in Colorado? De¬ 
scribe the process. 

6. How would you treat the lead button? If it is 
brittle what does it indicate? 

7. What is the best method of obtaining pure lead by 
the fire assav? 


IRON ORE ASSAY 


123 

8 . If the ore is an oxide or carbonate of lead, how 
would you mix the charge to flux it? 

9. How would you treat the lead ore if it contained 
copper? 

10. What is the general formula or dressing for a lead 
assay? 

11. How would you treat a complex sulphuretted ore? 

12. How would you cupel the lead button for precious 
metals? 

13. Describe the treatment of the ore to make the wet 
assay for lead. 

14. What is the effect of adding sulphuric acid? 

15. What is the effect of adding acetic acid? 

16. How is the acetate of ammonia added? 

17. In what form is the lead collected on the filter? 

18. What percentage of lead is the sulphate of lead so 
obtained? 

19. In the modification process, why multiply by .6832 
to get the percentage of lead? Explain it. 

DETERMINATION OF IRON IN AN ORE. 

1. The ores of iron most commonly used for the ex¬ 
traction of the metal, and as a flux for smelting furnaces, 
are the magnetic oxides, red and brown hermatite, specular 
ore, or spathic ores, and many times the amount of iron in 
a pyrites is required. 

2. Where the iron alone is required it is best to first de¬ 
termine the moisture. 

3. Then the silica, an insoluble residue, and lastly the 

iron. 

4. Take two or three grammes of the finely powdered 
ore, place it in a platinum dish, heat it to 100 c.; and weigh 
until the weight is constant. The loss in weight is the 
moisture. 

5. The ore is now oxidized with fuming nitric acid in 


124 


IRON ORE ASSAY 


the disli. Add a few cubic centimetres of strong snlphnric 
acid, and evaporate to dryness. 

6. The residue is now dissolved in hydrochloric acid, 
water added, and allowed to stand; then filtered into a boil¬ 
ing fiask, and washed. 

7. The indissoluble portion on the filter consists of silica 
and gangne, which should be well washed with hydrochloric 
acid and water, dried, cooled and weighed, and this is the 
silicates. 

8. To the filtrate add ammonia in excess. 

9. Also a few droi)s of yellow sulphide of ammonia; 
boil; decant repeatedly on the filter: finally bring the whole 
precipitate on the filter and wash with hot water. 

10. Redissolve the precipitate by pouring hydrochloric 
acid on it in the filter ; wash the filter with hot water, using 
a clean l)eaker to receive the filtrate. Again add ammonia 
and precipitate; boil; decant on a clean filter and wash as 
before. 

11. The alnmina, if present in the ore, will be precipitated 

with the oxide of iron on to the filter, which can be sep¬ 
arated from the iron by boiling the precipitate. 

12. To boil it, use a strong solution of potash for some 
time in a thin porcelain dish which dissolves out the alumina 
leaving the oxide of iron which may be caught on a filter, 
Avell washed with hot water; dried to 212 f., or to too c. 

13. Turn the filter and add the ashes to the precipitate 
and weigh; continue drying and weighing until the weight 
is constant, and the formula is Fe^, O3. 

14. To calculate the percentage of iron, if 2 grammes of 
ore were taken, multiplying the weight by five gives the 
percentage of oxide of iron. 

15. If 2^ grammes of ore were taken, then multiply the 
weight by 4 to find the percentage of oxide of iron. 

16. These weights of the oxides of iron multiplied by 
70 gives the percentage of metallic iron in the ore. 


VOLUMEl'RIC DETERMIXATIOX OE IROX BY 
R( )TASSIEM l^ERMAXGAXATE. 

1. Dissolve five i^ranimes of pure crystallized potassium 

permang’anate in distilled water by aid of heat, dilute to 

one litre and preserve in a stoppered bottle; keep it in a 

dark place. 1 he solution, if carefully kept, does not alter, 

but it is best to titrate it occasionallv. 

✓ 

2. \\'ei^2:h off accurately i gramme of thin, soft, clean, 
iron wire. Transfer it to a j litre fiask containing lOO c.c. 
of dilute sulphuric acid (one to five). 

3. Many chemists use a valve-flask for this purpose to 
prevent the oxidization of the iron during solution. 

4. But T prefer to dissolve without going to the trouble 
of prepaiing a valve-flask, and afterwards reducing the 
small amount of iron which may have been oxidized, by 
the addition of some granulated zinc. 

5. This reduction takes but a few minutes. When the 
iron is all reduced, which may be determinied by removing 
a drop of the solution on a glass rod, and testing it on a 
porcelain plate with a drop of ammonium-sulpho-cyanate 
solution (if the iron is all reduced to the proto-state the 
drop will remain colorless, while if any ferric oxide is pres¬ 
ent the drop will turn red, the depth of color depending 
on the amount of ferric iron present.) 

6. The contents of the flask are diluted by the addition 
of cold, distilled water, and the solution decanted off from 
the zinc to a large beaker, or an ordinary glass battery jar, 
which is less liable to breakage in stirring with the glass 

rod. 

8. The flask and zinc are well washed, the washings be¬ 
ing transferred to the jar and added to 10 c.c. of sulphuric 
acid. 

8. The solution is then diluted up to the 250 c.c. mark 


126 IRON ORE ASSAY 

and allowed to stand and settle so that the particles of car- 
bon present may deposit. 

9. Now take out with a pipette 50 c.c. of the clear and 
nearly colorless fluid (containing one-fifth of the iron 
weighed off) transfer to a 400 c.c. beaker, and dilute till 
the beaker is half full. It is always best to use the same jar 
and always fill to the same point so as to have the same 
bulk of solution. 

10. Place the beaker on a sheet of white paper, or bet- 
ter, on a sheet of glass, with a white paper underneath. 

11. Fill a Gay Lussac burette, divided into i-io c.c. up 
to zero, with a solution of potassium permanganate, of 
which take care to have at hand well mixed. 

Now add the permanganate to the previous solution, 
stirring all the while with a glass rod. At first the red 
drops disappear very rapidly, then more slowly. 

12. The fluid which, at first, was nearly colorless, grad¬ 
ually acquires a yellow tint. From the instant the red 
drops begin to disappear more slowly, add the permangan¬ 
ate with more caution, and in single drops, until the last 
drop imparts to the fluid an unmistakably reddish color 
which remains on stirring. 

A little practice will enable one to easily hit the right 
point. Now read off and mark the number of c.c. used. 
Use a float in your burette, and the reading off must be 
exact, the whole error not being more than i-io c.c. 

13. The amount of permanganate solution used should 
be about 20 c.c. Repeat the experiment with another 50 
c.c. of the iron solution. The difference between the per¬ 
manganate used in the cases should not be more than i c.c. 
If it is, make one more erperiment, and when the result is 
sufficiently near take the mean of the three as the standard. 

14. Now calculate what quantity of iron is represented 
by 100 c.c. of the permanganate. To this end, first divide 



IRON ORE ASSAY 


127 


the iron weig’lied off 1)y 5, and then ninltiply by 996, since 
soft iron wire contains, on an average, J per cent of carbon, 
and this gives the quantity of pure iron contained in the 
50 c.c. of the solution. 

15- Suppose we took 1.050 gnis. iron wire and used a 
mean of 21.3 c.c permanganate; 1,050- = .210; .210 times 
996—.20916 and then by rule of three:— 

.213: 20.916:: 100:? which equals .98,197. Therefore, 
100 c.c. permanganate ^.98197 pure iron. This experiment 
can be done with 200 grams of iron wire and the whole of 
the solution titrated, if desired. 

16. lo assay the iron ore grind it to a fine pulp, and 
weigh off one gramme accurately: dissolve it in sulphuric 
acid by heat: filter and wash. Make iqi the same bulk and 
titrate the solution the same as the standardizing solution 
and calculate accordingly. 

If there is a deficiency of free acid in either of the above 
named solutions, the fiuid may become a dark brown color, 
turning turbil and depositing a brown p.p., as if the perman¬ 
ganate were added too quickly: stirring too slowly may 
cause the same result. In such a case it is best to reject the 
whole thing and start anew. 

If the fluid reddened by the last drop of the solution of 
permanganate added loses its color again after a time, it 
need create no surprise or uneasiness, for a dilute solution 
of free permanganate cannot keep long without decom¬ 
posing; it does not affect the result. Do not add anew, 
thinking you have not finished the work. 

EXERCISES. 

1. For what purpose is iron mostly used in smelting 
ores ? 

2. What is first determined in an assay of iron ore? 

3. What is the second determination? 


128 


IRON ORE ASSAY 


4. What amount of ore is generally sufficient to make 
an assay? 

5. What would you first oxidize the ore with? 

6. After evaporating to dryness, how would you 
treat it? 

7. What does the insoluble residue consist of, and how 
would YOU treat it? 

8. Why would you add ammonia? 

9. Why add sulphide of ammonia? 

10. What effect does the boiling have on the precipitate?' 

11. If the ore contains alumina would it precipitate, 
and where would it be? 

12. How would you separate alumina from iron? 

13. How much of a heat would you give it before 
weighing? 

14. If two grammes of 1 e ore were used, how would 
the percentage of oxide of iron be calculated? 

15. If 2^ grammes were used, how calculate? 

16. How would you calculate the metallic iron? 

EXERCISES. 

1. How would you prepare potassium permanganate 
solution for volumetric assay of iron? 

2. How is it standardized? 

3. Is a valve-flask necessary? 

4. (a) In what state is the iron when dissolved in 
sulphuric acid? 

(b). What would you add to prevent its oxidizing? 

5. How is it tested to ascertain whether it is in a ferric 
or ferrous oxide? 

6. How is the solution ^ested before placing it into a 
beaker for titration? 

7. Would you wash the zinc and flask? 

8. To what degree is it diluted? 

9. What amount is taken for titration? 


129 


i IRON ORE ASSAY 

10. How is the beaker and jar arranged? 

11. Explain further the method of standardizing with 
. the burette. 

12. How does the coloration take place? 

13- How many experiments would you make before 
taking the mean? 

14. Make the calculation of the strength of the per¬ 
manganate solution. 

15- Suppose you take 50 c.c. of the solution and the 
mean was 21.3 c.c., make the calculation of the strength of 
the solution. 

CHROMIUM. 

There are several methods Hr the determination of 
chromic oxide (Cr2 O3) in an ore. Mitchelhs method by 
precipitation with nitrate of mercury is very good. But the 
following from Furman is as good as any: 

1. “Chromium is always determined as chromic oxide 
(Cr, O3), dark-green in color. 

2. “The only determinations of chromium which the 
metallurgical chemist will be called upon to make are in 
iron ores (especially chromic iron ore, known as chromite, 
or magnetite, which sometimes contain chromium), pig- 
iron and steel. 

3. “ORES.—Fuse from i.o to 2.0 grammes of ore with 
5 to 10 grammes of mixed carbonates of sodium and potas¬ 
sium and I gramme of sodium nitrate. Dissolve the fused 
mass in water and hydrochloric acid in slight excess, evap¬ 
orate to dryness, and determine the silica in the usual way. 

4. “To the filtrate from the silica add sodium carbonate 
until it is thoroughly alkaline, and then, without filtering 
out the precipitate, bromine water* until the solution is 
deeplv colored, stirring continually. 

5. “Now add 3 c. c. of pure bromide and heat for one 


130 ASSAY OF CROMATE OF IRON ORE 

hour, with frec[uent stirring, keeping the solution alkaline 
and gradually increasing the heat until it boils. 

Allow ’to boil for one hour, when the chromic oxides ' 
should all be oxidized to chromic acid. 

7. “Now filter (precipitate A) and wash thoroughly with 
hot water, washing first by decantation and then on the fil¬ 
ter until the filtrate runs through colorless. Should the ore 
contain a large amount of chronium, in order to insure its 
complete separation, wash the precipitate on the filter back 
into the beaker with the wash-bottle, bring the bulk of the 
solution u]) to about 100 c. c. with water, add 2 c. c. of bro¬ 
mine, and proceed as before, filtering through the same 
filter. 

8. “The filtrate will now contain all of the chromium as 
alkaline chromate, and probably some of the maganese. 

9. “The precipitate will contain all of the other constit¬ 
uents of the ore. Partially neutralize the filtrate with nitric 
acid, add from t to 3 grammes of ammonium nitrate, and 
evaporate until no odor of ammonia is perceptible. 

10. “Dilute with water, and should a precipitate form 
(precipitate B, probably Mn O^, Si^, Ai., ().j, and Ti O2), 
filter, and wash wdth warm water. 

II. “Acidify the filtrate with hydrochloric acid and 
saturate with sulphuretted hydrogen to reduce the chromic 
acid to sescpiioxide. Filted out the precipitated sulphur 
and wash. 

12. “In the filtrate precipitate the chromic hydroxide 
with ammonia, filter, wash, dry, ignite, and weigh the chro¬ 
mic oxide (Cr^ C)..,). To obtain the weight of the chromium 
multiply the weight of the precipitate by 0.68619. 

“Pig-iron, Steel, etc.—Dissolve the alloy in nitric and hy¬ 
drochloric acids, evaporate to dryness, dry and ignite the 
insoluble residue. Fuse the insoluble residue with mixed 
carbonates and proceed as above.” 





DETERMINATION OF MANGANESE 131 


DETERMINATION OF MACANESE. 

The best method and the one most used by western 
smelters is Volhard’s Volumetric process. 

1. Dissolve one gramme of the finely pulverized ore in 
2c. c. of hydrochloric acid, 4 c. c. of nitric acid, and 6 c. c. 
of dilute sulphuric acid, in a flask or casserole the same as 
for iron, and evaporate to copious fumes of sulphuric anhy¬ 
dride. 

2. Transfer the contents of the flask or casserole to a 
graduated 500 c. c. flask; wash into the flask with boiling 
water. 

3. Then add an emulsion of zinc oxide to the contents 
of the flask until the acid is neutralized and the iron is all 
precipitated as sesquioxide; violent shaking of the contents 
of the flask greatly facilitates the precipitation of the iron. 

4. After the precipitation is complete the oxide of zinc 
should be slightly in excess. The contents of the flask are 
then diluted with distilled water to the holding mark and 
after thorough shaking allowed to settle. 

5. After the oxide has settled so that the liquid is com¬ 
paratively clear, 100 c. c. or an equivalent part is drawn off 
by means of a pipette with distilled water, into the flask. 

6. The contents of the small flask are then ready for 
titration with a standard solution of permanganate of pot¬ 
assium. The titration is performed as follows: The per¬ 
manganate solution is dropped into the liquid in the flask 
from a burette, the contents of the flask being shaken after 
each addition of the permanganate solution, in order to fa¬ 
cilitate the settling of the precipitated maganese dioxide. 

From the amount of the precipitate and the rapidity with 
which the precij^itate is formed after each addition of per¬ 
manganate solution, the operator, after a little practice, will 


132 DETERMINATION OF MANGANESE 

be able to determine in what quantities it is safe to add the 
permanganate solution. 

7. The addition of permanganate should be continued 
until a faint pink color appears about the edge of the liquid 
after shaking, when held against a white background. 

8. The precipitation of the manganese is then complete, 
although it is safest, especially if the precipitation has occu¬ 
pied some time, to bring the, contents of the Hask again to 
boil and notice, after allowing the precipitate to settle, if 
the i)ink tint remains. 

9. If the color should have disappeared, another drop 
of permanganate is added, the flask shaken, and the precip¬ 
itate allowed to settle. If the color is permanent after set¬ 
tling the titration is complete. 

10. The same solution of permanganate of potassium 
used for the determination of iron may be used for this de¬ 
termination. 

11. In order to determine how much manganese one 
cubic centimetre of the permanganate solution is equal to, 

t 

it is only necessary to multiply its volume for iron by 0.2946 
to obtain its value for manganese; hence if the c. c. of the 
permanganate solution was equal to 0.010 gramme of iron, 
it would be equal to 0.002946 gramme of manganese. The 
reaction which takes place is as follows; 

3 Mn OXMn.^ O- =i5Mn O2. 

12. Some chemists prefer to filter off the precipitated 
oxides before diluting to 500 c.c., but this is unnecessary, 
as the precipitate occupies a small bulk although in its flac- 
culent state its bulk appears to be large, that it may be dis¬ 
regarded. Besides, the precipitate is difficult to wash, and 
the filtrate will give too low results. 

13. The zinc used must be pure and contain no man¬ 
ganese. 


DKTERMINAIION OF MANGANESE 


133 



1. Is chromium determined as an oxide or sulphide? 

2. With what is chromium combined in the ore? 

3. How will yon treat the ore and determine the silica? 

4. How is the filtrate then treated? 

5. What is the object of adding bromine? 

6. Why is the filtrate boiled? 

7. How is the precipitate A to be treated? 

8. In what form is the chromium now on the filter? 

9. What else may the precipitate contain? 

10. How is tire filtrate treated to obtain precipitate B? 

11. And how will yon treat this filtrate? 

12. After washing, drying, and weighing, how will you 
determine the chromiirm? 

13. How would you determine the chromium in pig- 
iron or steel? 


EXERCISES. 

1. What amount of the manganese ore would you take 
for the assay and what and how much acids are used? 

2. When transferred to a 500 c.c. flask, how is it 
treated? 

3. For what purpose would you add an emulsion of 
zinc oxide? 

4. AVhat would you do after the precipitation is com¬ 
pleted? 

5. After the liquid has settled clear what amount is 
taken for the assay? 

6. How would you titrate it? Explain the process in 

full. 

t 

7. What is the point of completion of the titration? 

8. Should it proceed slowly or quickly? 



134 DETERMINATION OF MANGANESE 

9. How would you terminate the titration? 

10. What solution of permanganate may be used? 

11. How is the calculation for the percentage of man¬ 
ganese made? 

12. Is it necessary to first filter the solution from the 
ore? If not, why not? 

13. Why should pure oxide of zinc be used? 


ASSAY OF ZIKC ORES 


135 


ASSAY OF ZINC ORES. 

Zinc, like other metals, has several methods of determi¬ 
nation, and each method has its advocates; but the follow¬ 
ing seems to be the simplest of them all and can be applied 
to any and every kind of ore indiscriminately: 

1. Take from 1 to 10 grammes, according to richness, 
treat with a mixture of sulphuric, nitric, and hydrochloric 
acids, and decompose in a porcelain dish on a sand bath; 
add some water and then excess of ammonia and also some 
ammonia carbonate. Keep warm for some time. 

2. Filter, wash with ammonia water until the drippings 
give no p.p., dark or white with ammonium sulphide. The 
impurities are now mostly left on the filter. 

3. To the clear filtrate and washings add ammonia sul¬ 
phide (which should be free from carbonates) as long as it 
precipitates and until the liquid smells of it. Stir, settle, 
filter, keeping the filter nearly full, and covered as much as 
possible. 

4. Wash with water containing ammonium sulphide, 
keeping the filter covered as before. When finally drain¬ 
ing, add a few drops of ammonium sulphide to prevent oxi¬ 
dation of p.p. and consequent loss of zinc. 

5. If the precipitate consists only of zinc 
sulphide it will be white, otherwise, as in pres¬ 
ence of silver, copper, nickel, or cobalt, it will 
be mixed with black, white, or yellow p.p., 
showing that cadmium is present or that some 
arsenic remained after the first treatment 
with ammonia, which might have been re¬ 
moved by addition of magnesia mixture. But 
in this assay these substances may be disre¬ 
garded. Manganese sulphide being of a pale 
flesh color is not conspicuous in presence of 


136 


ASSAY OF ZINC ORES 


zinc sulphide. However, if present, it may be 
removed by washing the p.p. with acetic acid, 
and afterwards displacing that by water. 

6. Now place a clean beaker under the filter, and, not 
entirely uncovering the latter, pour on the edge all around 
some warm dilute hydrochloric acid; this will dissolve the 
zinc sulphide, leaving copper, nickel, cobalt, cadmium, and 
arsenic sulphide unacted on, on the filter. 

7. When all the zinc is dissolved, again place a clean 
beaker under and pour the solution so far got,again on the 
same filter. 

8. When the liquid has passed, pour some more of the 
dilute acid on the edges and afterwards wash with water. 
The zinc is now in the filtrate. 

9. If there should be much sulphide of 
copper or other substances left on the filter 
it will be best to take the filter and contents, 
place it in a beaker, and then digest with 
warm dilute hydrochloric acid and then filter 
and wash, and add the filtrate and washings 
to the zinc filtrate above. 

10. We have now arrived at a point where the zinc in 
the solution can be determined either as an oxide by pre¬ 
cipitating it with a solution of bicarbonate of soda or volu- 
metrically. 

11. To precipitate as zinc carbonate, heat the solution 
to boiling, and add a crystal or two of potassium chlorate. 

12. Continue boiling, with the addition of small quanti¬ 
ties of the chlorate until any turbidity which may appear, 
clears up and a smell of chlorine is perceptible; (it may 
be necessary to add a few drops of hydrochloric acid, if 
not enough is present.) 

13. To the clear solution in a large covered beaker, add 
solution of sodium carbonate as long as it precipitates; heat 


ASSAY OF ZINC ORES 137 

to boiling for 20 minutes, and collect the precipitate on a 
filter. 

14. Wash until the drips no longer show a precipitate 
with nitrate of silver, or is neutral to test paper; dry, trans¬ 
fer the p.p. to a porcelain dish, burn the filter and add the 
ash; calcine at a red heat as long as the weight is incon¬ 
stant, cooling and weighing from time to time. The zinc 
is now the white oxide, yellow when hot, white when cold. 
Now calculate the percentage of zinc in the ore from the 
amount of ore used. 

16. Multiply the weight of the oxide by the coefficient 
80.26, and you have given the percentage of metallic zinc 
in the ore. 

In large smelting companies where the determination of 
zinc is often required the volumetrical method has the ad¬ 
vantage of being rapid, and is accurate enough for all 
practical work. 

The method here introduced is due to Fahlberg and re¬ 
quires a standard solution of potassium ferrocyanide. 

17. “A solution of which one cubic centimetre is equal 
to 0.010 gramme of zinc is the solution generally preferred 
by most chemists using this method. To prepare such a 
solution 45 grammes of pure potassium ferrocyanide (free 
from potassium ferricyanide) are dissolved in one litre of 
water and kept in a tightly stoppered green-glass bottle. 

18. “The solution will keep for some time without alter¬ 
ation, provided the bottle is well stoppered, and need not 
be tested more frequently than once every two or three 
weeks. It is best to make up the solution at least one day 
before using. 

19. “To standardize the solution, dissolve two portions 
of about 0.250 grammes each of pure zinc oxide (the zinc 
oxide should previously be ignited to convert any carbonate 
of zinc into oxide, and kept in a stoppered bottle so that it 


138 ASSAY OF ZINC ORES 

may not absorb carbonic acid or water from the air) in 5 
c.c. of pure hydrochloric acid, and add 50 c.c. of water in a 
beaker of about 300 capacity. 

20. “In order to have the same conditions present as 
near as possible as in the actual analysis, it is well to add 
ammonia in slight excess and then neutralize with hy¬ 
drochloric acid, using a small piece of litmus paper as an 
indicator. 

21. “When the solution has been brought to the point 
where it is just slightly acid, add an excess of 10 c.c. of 
pure strong hydrochloric acid, and dilute to 250 c.c. with 
cold distilled water. 

22. “The solution is now ready for titration with the 
ferrocyanide solution, which may be run in from a burette, 
rapidly at first, stirring from time to time. 

23. “If 0.2493 gramme of pure oxide of zinc were 
weighed out, it would require practically 20 c.c. of- the 
ferrocyanide solution to precipitate the zinc, provided the 
solution were normal; hence in this case about 18 c.c. may 
be run in before testing. 

24. “In order to test, the solution is thoroughly stirred 
with a glass rod, and a drop removed and added to a drop 
of a solution of pure uranium acetate on a porcelain plate. 

25. “The uranium-acetate solution is prepared by dis¬ 
solving sufficient uranium acetate in water to give a pretty 
strong solution, and clarified by adding a few drops of 
acetic acid. This solution should be kept in a small stop¬ 
pered bottle in a dark place, as it is decomposed by the ac¬ 
tion of sunlight. As long as there is not an excess of fer¬ 
rocyanide in the solution the drop of uranium acetate will 
retain its yellow color; as soon as the ferrocyanide is in 
slight excess it will turn a light brown, the shade being 
darker according to the amount of ferrocyanide in excess. 
The titration should be proceeded with, testing after the 


ASSAY OF ZINC ORES 


139 

addition of each drop of ferrocyanide towards the last of 
the operation, and stirring well before testing, until a slight 
brownish tint is produced on the drop of uranium acetate. 
The amount of ferrocyanide used is then noted, and tlie 
value of one cubic centimetre calculated. The duplicates 
should not differ by mere than one-tenth of a cubic centi¬ 
metre. 

26. “The precautions to be observed are: To have 
about the same bulk of solution in all subsequent titrations; 
to have the same amount of hydrochloric acid present; to 
have the standard solution at about the same temperature, 
and to have the zinc solution comparatively cool. ' If too 
large an excess of acid is present, or if the zinc solution is 
too warm, a decomposition will ensue, resulting in the lib¬ 
eration of chlorine. This may be seen by the solution turn¬ 
ing yellow or yellowish-green. The precipitate should al¬ 
ways be white, and the solution colorless or nearly so.” 

EXERCISES. 

1. What amount ol zinc ore would you take for an 
assay, and with what acids would you treat it? 

2. How proceed after digesting it with acids? 

3. Through what process would you put the filtrate? 

4. What should be done while it is cn the filter? 

5. What is the appearance if it contains silver, copper, 
arsenic, or cadmium? 

6. What is the next step in the assay? 

7. Wdiat is left on the filter when all the zinc is redis¬ 
solved? 

8. Where is the zinc when the liquid has all passed 
through the filter? 

9. How is the substance left on the filter treated? 

10. At what point has the assay now arrived? 


140 ASSAY OF ZINC ORES 

11. How is the filtrate treated to precipitate as zinc 
carbonate? 

12. For what purpose is chlorate of potash now added? 

13. Why would a solution of sodium carbonate be 
added? 

14. How would you treat the precipitate on the filter? 

15. In what form is the zinc at this stage? What is its 
appearance when hot? When cold? 

16. How is the amount of metallic zinc determined from 
the oxide? 

17. How is the standard solution of potassium ferro- 
cyanide prepared? 

18. How must it be kept? 

19. How is this solution standardized? 

20. What is necessary to have the same conditions in 
the analysis? 

21. When the solution is brought to the point where it 
is just slightly acid what is added, and to what is it diluted? 

22. What is the next step? 

23. If 0.2493 of a gramme of pure zinc were weighed 
out, how many c.c. of the ferrocyanide solution would it 
take to precipitate the zinc? 

24. How is it tested? 

25. How is the uranium acetate prepared? 

26. What are the precautions in this case? 


ASSAY OF NICKEL 


141 

ASSAY OF NICKEL AND COBALT ORES. 

The analysis of nickel and cobalt ores has been consid¬ 
ered one of the most tedious of any that falls to the lot of 
the assayer, owing to the separation of the two metals which 
are always associated together. But of late years the pro¬ 
cess has been somewhat simplified. 

I have examined the various methods by different au¬ 
thors and find Aaron s to be the most satisfactory of all. 
By the use of his potassium xanthate he is enabled to throw 
down the cobalt xanthate first. I have made several analy¬ 
ses of nickel ore by this methc and ^nd it less complicated 
than any other which I have used. 

In order to make this assay it is necessary to prepare a 
solution of potassium xanthate which Mr. Aaron uses for 
the assay of copper by standardizing it the same as the 
cyanide of potassium solution; also the carbonate of zinc 
solution. 

I. “Preparation of the Potassium Xanthate Solution. 
Dissolve two ounces (troy) of caustic potassa in about a 
quarter pint of 95 per cent alcohol in a stoppered bottle; 
add carbon disul])hide, little by little, as long as a curd is 
produced, a hissing noise heard, and a partial vacuum is 
formed in the bottle, as evinced by the stopper resisting ex¬ 
traction. Shake the bottle occasionally. When the above 
effects cease, and a further addition of the disulphide causes 
expansion, which may expel the stopper, while its odor is 
no longer neutralized but becomes disagreeably percepti¬ 
ble, and a yellowish fiiiid appears which partly liquifies the 
previously almost solidified contents of the bottle, pour the 
whole into a dish and leave it to spontaneous evaporation 
in a dark, cool place for twelve hours or more, the dish will 
then contain a plastic mass; dissolve tliis in six pints of 
cold, pure water. Let llie ..soJution stand a short time to 


142 


AND COBALT ORES 


deposit any excess of disulphide, and then bottle it in com¬ 
mon beer bottles (‘‘black bottles”), which keep in a dark, 
cool place. 

“About 50 c.c. of the solution thus made will precipitate 
0.5 of a gramme of copper; it may be diluted, if so pre¬ 
ferred for very close work, so that it will require 100 or 200 
c.c. for that quantity of copper. If the alcohol is not al¬ 
most saturated with caustic potassa, the curdy mass spoken 
of may not appear until evaporation has taken place. The 
compound may be made in an open dish, the carbon di¬ 
sulphide being dro]3ped into the alcoholic solution of po¬ 
tassa until that no longer reacts alkaline. The crystals of 
potassium xanthate are white; they may be washed with 
ether, and may be preserved indefinitely, and dissolved in 

water or in alcohol for use. Caustic soda may be used in 
place of potassa; the sodium xanthate forms orange-colored 
crystals. ,, „ 

"To Make the Zinc Carbonate, or rather hydro-carbon¬ 
ate, dissolve zinc sul])hate in water, and filter it; also dis¬ 
solve sodium or potassium carbonate in water. Filter the 
latter into the former until nearly but not quite all the zinc 
is thrown down; collect the p.p. on a filter and wash it. The 
filtrate should still give a p.p. on addition of the soda solu¬ 
tion, in order to guard against an excess of soda which 
would be difficult to wash out of the zinc carbonate. Keep 
the carbonate moist in a wide-mouthed jar or bottle. 
Prolrably zinc oxide would answer as well, and would be 
more convenient, because it would not cause effervesence. 

2. To make the assay of nickel and cobalt the ore may 
contain besides these metals, iron, manganese, zinc, copper, 
gold, silver, lead, bismuth, antimony, arsenic, calcium, bar¬ 
ium, strontium, aluminum, magnesium, silica, and sulphur. 

Should it also contain mercury, telurium, or selenium, 
these are easily expelled by roasting the weighed assay be¬ 
fore proceeding further. ,, 


ASSAY OF NICKEL 143 

3. Powder the ore very finely; take one to two and one- 
half grammes according to the richness of the ore. 

4. Digest in plenty of nitrohydrochloric acid, the nitric 
in excess. Let all sulphur be dissolved, or remove the 
drops from the sufficiently cooled liquid, picking them out 
and rinsing them in water which falls into the solution. 

,5. Add a little sulphuric acid, unless the ore contains a 
good deal of sulphur or copper or iron pyrites; evaporate 
nearly to dryness; cool, dilute, filter, and wash with hot 
water until the drippings give a dark p.p. with ammonium 
sulphide, by testing a drop of it on white porcelain. 

7. “If the volume of liquid is now conveniently large, 
reduce it by evaporation. 

8. “Add solution of caustic potassa or soda very care¬ 
fully, not producing any distinc^^ p.p., although in many 
cases a slight turbidity, but the liquid must remain slightly 
acid to test paper. 

“If too much alkali be added, it must be counteracted by 
a drop or two of hydrochloric acid; it is better to use no 
alkali than too much. 

10. “Now add moist precipitated zinc carbonate; stir, 
and continue adding the carbonate until a considerable ex¬ 
cess of it remains unchanged in the liquid, which may be 
slightly warmed. 

11. “If the assay contained no copper, test a minute 
drop on white porcelain, with a drop of solution of potas¬ 
sium sulphocyanate; when this gives no red or pink tinge, 
the iron is all down. 

12. “If copper is present, test for that, in the same way, 
with potassium ferrocyanide, which will give a brownish 
red color as long as any copper remains in solution. 

13. ‘‘As the iron goes down first, it is not necessary to 
test for that when copper is present; when the copper is all, 
or nearly all down, a bluish or greenish p.p. may be pro- 


144 


AND COBALT ORES 


duced by this test, which must not be mistaken for the blue 
which the persalt of iron would produce; it is caused by 
cobalt or manganese. 

14. “When the copper is all down, filter, and wash with 
hot water as long as the drips give a p.p. with solution of 
potassium xanthate, (Return these tests to the filtrate.) 

15. “For a final test of the washings, place a drop on 
porcelain and add a drop of ammonium sulphide; it should 
not blacken. 

16. “Now warm the liquid to about blood heat, or a 
little higher, and add solution of potassium xanthate, at in¬ 
tervals,, as long as it is seen to produce a yellow or a green¬ 
ish p.p. Keep the liquid warm, and let it stand some time, 
stirring occasionally, until it clears tolerably. Try a little 
more xanthate; it will probably make a white p.p. of zinc 
xanthate, which, however, either changes its color or dis¬ 
appears, being either converted to nickel or cobalt xanthate, 
or dissolved. At last, filter a little of the solution on a filter 
which has been exactly balanced with another on a fine 
balance. Test the filtered liquid with potassium xanthate; 
if any yellow or green p.p. forms, return the test to the main 
solution, and add more xanthate to that, but avoid a great 
excess. 

17. “When no more p.p. forms, or only a white one 
which dissolves, make a final test with a drop of ammonium 
sulphide; it should give no black p.p. although a white one 
of zinc, perhaps tinged by pinkish manganese sulphide. 

18. “Collect the p.p. after letting it settle, on the same 
filter that was used in testing; any p.p. which may adhere 
to the side of the beaker must be removed by the aid of hot 
water and a rubber-tipped glass rod; a short piece of pure 
rubber tube on the end of the rod will answer. Wash sev¬ 
eral times with rather hot water. 

19. “Place a clean beaker under the filter, and leach 


ASSAY OF NICKEL 145 

the p.p. with slightly diluted ammonia until that passes col¬ 
orless, and a drop of it gives no p.p. with a drop of acetic 
acid (or very dilute sulphuric) enough to destroy the smell 
of the ammonia. Add the drop to the filtrate if it gives 

a p.p. 

20. “Remove the beaker containing the ammoniacal so¬ 
lution of nickel xanthate, and wash the cobalt xanthate on 
the filter with hot water containing a little ammonia, until 
the filter is clean and the p.p. ceparates well from it under 
the jet. 

21. “Dry the cobalt xanthate, still on the filter, and the 
counterpoise filter with it, on the waterbath; cool and weigh 
it, on the filter, putting the counterpoise filter on the weight 
pan; return both to the water bath for ten minutes; cool 
and weigh again, and so until it weighs twice alike. 

22. “The cobalt xanthate should be of a 
dark pure but not brilliant green color; if 
mixed with orange yellow, it contains a con¬ 
siderable proportion of copper; when cal¬ 
cined, it should be black, not green, which in¬ 
dicates the presence of zinc, and if it gives a 
blue solution with ammonia, copper is pres¬ 
ent; the copper may be removed thus: Re¬ 
dissolve the calcined p.p. and the burned fil¬ 
ter, in aqua regia; dry with addition of hy¬ 
drochloric or sulphuric acid; take up with 
water and a little of the same acid; digest 
warm with a piece of zinc, keeping the liquid 
distinctly acid so that bubbles rise from the 
zinc; the copper will be precipitated; remove 
the zinc and copper, nearly neutralize the 
liquid by potassa, reprecipitate the cobalt by 
potassium xanthate, wash, dry, and weigh. 

“To the ammoniacal solution of nickel xanthate, 


23- 


AND COBALT ORES 


146 

add very dilute sulphuric acid until the greater part of the 
nickel xanthate is reprecipitated, but the liquid still smells 
of ammonia; then add acetic acid until the liquid has a 
slight acid reaction; stir, to curdle the p.p.; let stand for 
some time, stirring occasionally. Add a little potassium^ 
xanthate, and, if it produces a p.p., add as much more as 
may be necessary but avoid great excess. Collect on a 
counterpoised filter, cleaning the beaker as with the co¬ 
balt; wash with hot water until the p.p. cleaves readily from 
the filter under the jet; dry on the water-bath, cool, weigh, 
and so on until it weighs twice alike. 

24. “Each of the xanthates contains 19.6 per cent of 
metal, or, the weight multiplied .196 is the weight of the 
nickel or cobalt. The filtrations may be greatly facilitated 
by connecting a foot of rubber tubing to the beak of the 
funnel and letting it hang downward, the end in the re¬ 
ceiving vessel. This should not be done while leaching 
with ammonia. 

“In certain circumstances, believed to be 
the presence of arsenic in the solution, the 
precipitation of copper by zinc carbonate is 
not quite complete; if, however, there is suffi¬ 
cient iron present, the difficulty no longer ex¬ 
ists; hence, if a little copper should remain 
in solution, notwithstanding an excess of zinc 
carbonate, add a little iron per-chloride, as 
nearly neutral as may be, and then more zinc 
carbonate if necessary. If the ore is known to 
contain arsenic, with Init little iron, while cop¬ 
per is also present, it may save trouble to add 
a little metallic iron to the assay in the first 
instance. All iron in the solution must be in 
the form of a persalt, and it will be so if 
enough of nitric acid be used in making the 


147 


ASSAY OF NICKEL 

solution. In the treatment with zinc carbon¬ 
ate the liquid may be slightly warmed, not 
highly heated, or nickel and cobalt will also 
come down. 

“The potassium xanthate made, as directed for the cop¬ 
per assay, with alcohol of 95 per cent or thereabout, is a 
little alkaline, and becomes more so by keeping; in this 
state it is not fit for this assay. 

“Before using it, test it with faintly reddened litmus 
paper; if it blues that, add some very dilute sulphuric or 
hydrochloric acid, not strong enough to cause turbidity, 
or, if it does, warm the liquid until clear. 


148 


RESUME OE OPERATIONS' 


RESUME OE OPERATIONS.. 

1. “Dissolve; dry; take up; filter. 

2. Treat with zinc carbonate; filter. 

3. Precipitate with potassium xanthate; filter. 

4. Leach with ammonia. 

5. Dry and weigh cobalt xanthate. 

6. Recover nickel xanthate by acid; filter, wash, dry,, 
weigh. 

7. Multiply weights by .196 for metal. If the greatest 
possible accuracy is required, see Fresenius’ Quan An, or 
send the assay to an analytical chemist. 

Sometimes a little of the cobalt is found mixed with the 
recovered nickel xanthate. To insure a perfect separation, 
collect the recovered nickel xanthate on tlie original filter, 
dissolve it again in ammonia and again recover it by acid 
as before, then collect it on a new counterpoise filter, dry 
and weigh. The whole of the cobalt will be on the first 
filter.” 

All the instructions must be followed out minutely, es¬ 
pecially in preparing the zinc carbonate and xanthate so¬ 
lution, as well as the details of the operation, or no satis- 
factorv results can be had. 


EXERCISES. 

1. How would you prepare a solution' of potassium* 
xanthate? 

2. With what substances may nickel and cobalt be as¬ 
sociated in the ores? 

3. How is the ore prepared and what amount is takeu- 
for the assay? 

4. What acid is used to digest it? 

5. What is added if the sulphates are in the. ore?. 


RESUME OE OPERATIONS 


149 

6. After cooling, diluting, filtering, and washing, what 
are the drippings tested with, and for what purpose? 

7. What is done if the volume of liquid is too large? 

8. What is added to the filtrate? Must it be alkaline 
or acid? 

9. What is to be done if too much alkali is added? 

10. What is next added to the liquid? For what pur¬ 
pose? 

11. What is it now tested for? With what? 

12. With what is the test for copper made? 

13. Is it necessary to test it for iron when copper is 
present? 

14. What is done when the copper is all down? 

15. How are the washings tested? What are they 
tested with? 

16. What is next done with it? 

17. When no more precipitate forms, or only a white 
one, which dissolves, what would you test it with? 

18. What is now done? 

19. With what is the precipitate leached? 

20. What does the filtrate now contain? 

21. What is on the filter? How would you treat it? 

22. What color is the cobalt xanthate? 

23. What is now done with the nickel xanthate? 

24. What per cent of the metal does each of the xan- 
thates contain? 

25. How is it determined? 


MERCURY 


150 


MERCURY. 

The distillation methods described by Fresnius, Mitchell, 
Rickette, Aaron, and others are good, especially if the per¬ 
centage of mercury is large 

1. For rich ores I frequently take as much as four oun¬ 
ces of the ore and mix it with five ounces of iron filings, 
and half an ounce of lime. (Iron filings in large excess are 
preferable, as it renders the mass more porous, and facili- 
tates'the distillation. 

2. Put in a clean iron retort and place it in a furnace 
with the iron pipe leading out over a receiving dish of cold 
water, wrapped with a strong cloth which should be fre¬ 
quently saturated with cold water, or better still, keep a 
small stream of water running from a faucet over it. 

3. Heat very gradually at first, with a red heat to finish. 

When the distillation is completed, which may be known 

by tapping the iron pipe with a hammer and no more mer¬ 
cury is seen to come over, shut off the fire or remove the 
retort from the furnace*and let it stand until cold; discon¬ 
nect the retort, cover, and pipe, and wash out completely 
into the receiving dish; pour off the greater part of the 
water. 

4. Add a little potash solution to clean and facilitate the 
collection of mercury by one mass by rubbing it with the 
fingers; extract the remaining water with blotting paper, 
dry, and weigh, and calculate the percentage. 

5. The assayer is frequently called upon to make an as¬ 
say of very low grade ore running from two-tenths to one 
per cent of mercury. 

For ores of this character I take the piece of combustion 
tubing about twelve or fourteen inches long annd closed at 
the left-hand end. Introduce a weighed quantity of the 
finely pulverized ore. 


MERCURY 


151 

6. The ore introduced should be mixed with iron filings 
and lime. Shake the mixture down into the closed end. 
On top, near the right-hand end, place a very small plug of 
ignited asbestos. Lay the tube in a horizontal position and 
tap it so that an open passage will be left over the ore. 

7. Into the right-hand end of the combustion tube in¬ 
troduce a spiral gold foil of known weight, also a rubber 
cork connected with a glass tube. This small tube should 
be about 18 inches in length, and should be bent up in the 
form of an L at the open or right-hand end. It can be kept 
cool by wrapping around it a cloth saturated with col l 
water. This second tube is to catch any mercury which 
might pass the gold foil. 

A 

After the apparatus is connected, heat the left-hand end of 
the tube containing the ore, but keep the right-hand end of 
the tube, containing the gold spiral, cool. 

Should any mercury condense in the combustion tube, it 
can be driven forward by moving the flame of the burner 
towards the right. 

I find it a good plan to lay the combustion 
tube in a combustion furnace with a little 
charcoal around it, and then when the tube is 
heated it will keep hot and prevent the re¬ 
turn of the mercury to the left-hand end of the 
tube. 

8. After all the mercury is distilled, which will require 
from 15 to 30 minutes, remove the heat and allow the tube 
to cool. When cool, disconnect the apparatus, examine the 
small tube, and if it contains any mercury, wash it out with 
the wash-bottle, add to the gold spiral, and weigh. 

The increase of the weight of the gold will represent the 
mercury. This process, well performed, gives excellent re¬ 
sults, when the ore is as low as two-tenths of one per cent. 
A small amount of rich ore, one or two grains, may be as- 


MERCURY 


152 

sayed in the same way. There are several methods of de¬ 
termining mercury in wet way, but they are extremely tedi¬ 
ous, and far from accurate. 




ASSAY OF ARSENIC 


153 


ASSAY OF ARSENIC. 

The best method for the determination of arsenic is that 
devised by Dr. Richard Pearce, of Denver, Colorado. It is 
the most accurate and rapid method we have. 

1. The finely powdered substance for analysis is mixed 
in a platinum crucible with from six to ten times its weight 
of a mixture of equal parts of sodium carbonate and potas¬ 
sium nitrate. 

2. The mixture is then fused gradually until it flows- 
smoothly. It is then cooled and extracted with water 
warmed in the crucible and filtered. 

3. The filtrate contains the arsenic combined with¬ 
al kalies. 

4. Acidify with nitric acid and boil; cool; neutralize al¬ 
most exactly by ammonia, so that previously reddened lit¬ 
mus paper shows alkali in half a minute. If not clear, filter. 

5. Add a neutral solution of nitrate of silver in slight 
excess. 

6. Stir to coagulate the precipitate which is of a brick- 
red color. Filter; wash the precipitate with cold water. 
Dry, scorify the precipitate with lead and cupel the button.- 

Test the filtrate with silver nitrate, dilute 
nitric acid and ammonia to again neutralize 
in order to see that the precipitation is com¬ 
plete. The second neutralization is always 
necessary when the amount of arsenic is 
large, as nitric acid is set free in the reaction 
between the alkaline arsenite and silver nitrate 
according to the following: 3 (Ag NO3) -|- 
Na H, As O4 = Ag3 As O, -|- Na N03 -|- 2 
(HNO3). 

7. If the ore contains any chloride—silver chloride,, 
etc., (which is seldom the case), or if the water or soda used 


ASSAY OF ARSENIC 


154 

contained chlorides, then instead of at once scorifying the 
,p. p. ponr dilute nitric acid over it while on the filter to dis¬ 
solve the silver arsenite and separate it from the silver chlo¬ 
ride, which will remain on the filter. 

8. To the liquid add enough of hydrochloric acid to 
precipitate all the silver on it as chloride. 

9. Collect the chloride on a filter, wash with hot water, 
dry, and scorify with lead, adding a little soda. 

10. The weight of the silver obtained multiplied by 

..2315 gives the weight of arsenic in the assay. 

In preci])itating arsenic with silver nitrate, 

the best way, although it requires a long time, 
is to acidulate the alkaline solution with ni¬ 
tric acid; dilute largely if the substance con¬ 
tains sulphur, add a sufficient quantity of sil¬ 
ver nitrate—which need not be neutral—then 
excess of ammonia to redissolve any p. p.,and 
finally evaporate withoct boiling until the 
odor of ammonia is gone, when the silver ar¬ 
senic will come down. 

EXERCISES. 

MERCURY. 

1. How is cinnabar ore prepared for an assay? 

2. If an iron retort were used how is it arranged? 

4. How is the mercury cleaned and collected? 

5. How would you assay a low-grade ore? 

6 . How is the apparatus arranged? 

7. How is it charged? 

8. How is the mercury collected and saved? 


ARSENIC 


155 


ARSENIC. 

1. With what and how is arsenic ore prepared for an 
assay ? 

2. How is the mass treated after fusing? 

3. Where is the arsenic after filtering? 

4. How is the filtrate then treated? 

5. What is now added? For what purpose? 

6. How is the p. p. collected, and how is it treated? 
Would you test the precipitate? Write the reaction 

which has taken place. 

7. What is done if the ore contains any chloride? 

8. What is done if further p. p. is found? 

9. How is the silver button collected and treated, and 
the amount of arsenic in the ore estimated? 

10. Why multiply by .2315? 



ASSAY OF ANTIMONY. 



ASSAY OF ANTIMONY. 

1. Weigh out a suitable quantity of the ore and fuse it 
with 4 parts of cyanide of potassium (if this is not at hand 
equal parts of borax and carbonate of soda will do); place 
it in a small clay crucible and fuse it until it flows smoothly. 
Pour it into an assay mold, or cool it in the crucible, break¬ 
ing the pot to extract the button. 

2. Clean the button and place in a dilute solution of hy¬ 
drochloric acid, as it will not bear the hammer. 

3. If the ore contains no lead or other metals the button 
may be weighed at once as metallic antimony. 

4. But if it contains lead or other metals, pulverize or 
flatten it with the hammer and boil it in diluted nitric acid. 

5. This will leave nearly all the antimony in a white 
powder, which, when washed on the filter, dry and fuse 
again with cyanide of potassium. 1 his will give you a but¬ 
ton of pure antimony, miles tin be in the ore, which is not 
likelv. 

6. Second Method.—Ihe ore can be fused with about 
six parts of equal quantities of sulphur and soda in a tight¬ 
ly covered crucible. When sufficiently fused and the great¬ 
er part of the sulphur burned out, cool, and extract the but¬ 
ton with hot water, which dissolves the antimony. 

7. Filter; to the filtered solution add hydrochloric acid 
to acid reaction; collect the precipitate on a filter and wash 
into a beaker. 

8. Then pour on the filter a solution of nitre, dry and 
burn the filter, adding the ashes to the precipitate. 

9. Then treat the whole mass with nitric acid until all 
sulphur is oxidized. Evaporate nearly to dryness; cool; 
dilute with water and filter. 

10. The antimony remains on the filter in a pure state, 


ASSAY OF ANTIMONY 


157 

-which fuse with cyanide of potassium as before; extract 
button, clean, weigh, and calculate the percentage of me¬ 
tallic antin', ony. 


158 


ASSAY OF BISMUTH 


ASSAY OF BISMUTH. 

1. Bismuth ore may be assayed much the same as lead’ 
by mixing the finely powdered ore with equal parts of cy- 
annide of potash and bicarbonate of soda. 

2 . If the ore contains any copper, add sulphur to keep 
the copper out of the button. 

3. If the ore contains no sulphur or arsenic add one 
part of sulphur and a little charcoal with three nails to the 
dressing. The following is a good charge for an assay: 

4. Ore . I Part. 

Sulphur . I ” 

Charcoal . i ” 

Cover with salt and smelt in the crucible the same aS' 
lead, and calculate the percentage of bismuth. 

5. Cupel the button for gold and silver. If much of 
either metal is in the button, deduct it from the weight of 
the button. 

6. Lead and antimony, if present, will go into the but¬ 
ton. If the ore is poor in bismuth add some litharge to the 
dressing to collect the bismuth, using 40 per cent of litharge 
for an ore containing 10 per cent of bismuth. In such a 
case make the following charge: 

7. Ore . I Part. 

Litharge .4-10 ” 

Sulphur . I ” 

Charcoal . ^ ” 

Cover with salt and add three nails. 

8. If the ore is rich in copper and it comes down with- 
the lead and bismuth, making it hard, flatten it out and boil' 
in dilute nitric acid. It will dissolve the bismuth, lead, cop¬ 
per and silver. 

9. If there is any tin or antimony in the ore it will be 
insoluble. Filter and add enough sulphuric acid to the fil- 









ASSAY ()!' r>ISMYTH 


159 

ti'Lte to precipitate the lead; boil the acid down; cool; add 
water and boil. If there is any soluble matter let it settle; 
decant upon a filter: boil several times with water and a 
little sulphuric acid, decanting- upon the filter, washing 
slii fitly. 

I ). To the filtrate add excess of ammonia carbonate 
am' heat to boiling. Filter and wash with ammonia water 
unt l that passes colorless; dry on filter; smelt the p. p. with 
filt( r and all together with a little borax glass and potas- 
sii • 1 cyanide. Separate the button from the slag; weigh 
an(’ calculate the percentage of bismuth. 

EXERCISES FOR AXTHIONY. 

[. l iow would you make a charge for antimony ore? 

2. Flow may the button be cleaned? 

3. What is done if the ore contains no lead or other 
metals? 

.p How is it treated if it contains lead? 

5. (a) How will it leave the antimony after boiling 
with nitric acid? 

(b) W'hat would you then do with it? 

6. How is the ore treated by the second method of as¬ 
say ? 

7. What is added to the filtered solution? For what 
purpose? 

8. How may the filter and contents be treated? 

9. What is done with the whole mass? 

10. Where is the antimony after the second filtering? 


i 6 o 


ASSAY OF BISMUTH 


BISMUTH. 

1. (a) How can bismuth be assayed? (b) With what 
is it fluxed? 

2. What is the manner of fluxing if it contains copper? 

3. If no sulphur is in it, what is added? 

4. What are the proportions of the charge? 

5. If it contains either gold or silver, how are they sep¬ 
arated? 

6. What is the method of treating a low-grade ore? 

7. In that case what is the charge? 

8. (a) When the ore is rich in copper what is the ap¬ 
pearance of the button? (b) How is the button treated,, 
and what is the effect of dissolving it? 

9. What is done if the ore contains tin? 

10. How is it treated? 

11. How would you treat the filtrate and calculate the 
percentage? 


DETERMINATION OF SULPHUR i6i 


DETERMINATION OF SULPHUR. 

This method for the determination of sulphur was first 
proposed by M. W. lies, and, I believe, has been adopted 
by all the Western smelter and mining companies, although 
it is almost impossible for any two chemists to obtain re¬ 
sults that will agree by this or any other method. Fresenius, 
who is the recognized authority, declares that this method 
is subject to error from 2 to 3 per cent, but it has not been 
improved upon. 

1. C. H. Aaron recommends fusion of the powdered ore 
with nitre and alkaline carbonates, which may do for ord¬ 
inary sulphurets, such as pyrites, etc. 

2. For the determination of rich sulphur ore, especially 
that which is imported from Japan, it will not do, as the 
nitre and sulphur with any of the carbonates will form an 
explosive equal to gunpowder, and when fusion takes 
place an explosion will invariably occur. 

3. The best decomposing agent is caustic potash alone, 
which has been prepared with alcohol. This comes in 
sticks. 

4. Weigh out one to two and one-half grammes of the 
finely powdered ore, according to richness. Fuse eight to 
ten parts of the caustic potash first in a platinum dish, then 
partially cool and brush the ore on top of the partly fushed 
potash; heat from 5 to 20 minutes until it is completely de¬ 
composed, using a spirit lamp for this purpose, as coal gas 
often contains some sulphur compounds. 

5. Remove the dish and allow it to cool ; as soon as cold 
dissolve the mass out with warm water into a beaker, and 
when it is all transferred to the beaker,bring the contents 
to a boil, and filter through a rild:)ed filter paper. 


i 62 


DETERMINATION 


6 . Wash with boiling water until the washings come 
through free from sulphides or sulphates. Add 20 to 40 
c.c. of bromine water to the filtrate and heat to about 90 
degrees Centigrade, and then acidify with hydrochloric 

acid. , 

7. If the substance contains silica it will now be in 
solution and must be removed by evaporating to dryness, 
heating and dissolving with water and hydrochloric acid 
and filtering off the silica thus rendered insoluble. 

8. To the filtrate from the silica, after boiling, add a 
solution of boiling Ijarium chloride until all of the sulphur 
is precipitated as barium sulphate. 

By heating the solution of barium chloride before add¬ 
ing it to the -solution the barium sulphate is precipi^:lted 
almost immediately. 

9. This would not be the case if a cold solution of 
barium salt were used. After the addition of the ba'i.im 
chloride the solution is brought to a boil and then ren: , . ed 
to a warm place and allowed to settle. 

10. After settling, it is filtered and washed thoroughly 
with boiling water, and then with a few drops of di'nte 
hydrochloric acid dropped around the edge of the filter, 
and again twice with hot water. 

11. It should be washed until the washings no longer 
give a precipitate with silver nitrate solution. 

12. The precipitate is now dried together with the filter 
paper, and when dry transferred to a platinum crucible and 
gently rolled with the fingers. 

13. The crucible is placed on a sheet of glazed paper or 
a large watch glass, so that any particles which may tly 
over the sides of the crucible may be recovered. 

14. After cleaning the ])aper it is rolled up and placed 
on the lid of a platinum crncil^le and burned by holding 


OF SULPHUR 


163 

the platinum over the name of the burner. The ash of the 
filter-paper is then added to the contents of the crucible, 
and the whole ignited to redness over a blast lamp. 

15. The crucible is then cooled and its contents should 
be found perfectly white. The precipitate is now transfer¬ 
red from the crucible to the watch glass pan of the balance 
and weighed. 

16. The weight of the barium sulphate less the known 
weight of the filter-ash, multiplied by 0.13734, will be the 
weight of the sulphur present in the amount of ore or sub¬ 
stance taken for assay. 

When silica is not present the evaporation to dryness of 
the filtrate from the solution of the fusion may be dispensed 
with, thus saving much time. This, method is universal in 
its application, but requires much time, and where great 
accuracy is required it should be done in duplicate. 

The following method from Furman is frequently used 
in lead and copper smelting works for the determination 
of sulphur, and whilst it is not as accurate as the method 
previously described, it has the advantage of being rapid, 
and consequently would be used where time for an accurate 
determination is not available: 

“Treat one gramme of ore in a flask (about 200 c.c. ca¬ 
pacity) with three to four grammes of potassium chlorate 
and 7 c.c. of nitric acid, the acid being added as follows: 
About 3 c.c. at first, and then i c.c. from time to time. 
When all the acid has been added, heat to boiling on a 
sand-bath and evaporate of? the excess of acid. All but 
about 2 c.c. of acid should be expelled. The potassium 
chlorate and nitric acid oxidize the sulphur in the ore, and 
in the case of a heavy sulphide more potassium chlorate 
may be necessary. The solution, after boiling, should show 
no undecomposed particles of sulphides and no globules of 
yellow sulphur, which will sometimes form if the oxidation 


DETERMINATION 


164 

has been imperfect. Remove from the source of heat, dilute 
with about 50 c.c. of water, and add a saturated solution of 
sodium carbonate in excess. The sodium carbonate pre¬ 
cipitates the lead, iron, etc., and the excess is added to de¬ 
compose the sulphates of lead and calcium which may have 
formed during' the solution. Boil for from 30 minutes to 
one hour, adding water from time to ‘time to keep the bulk 
of the solution about the same. Eilter through a fluted 
filter into a l^eaker, and wash until the washings no longer 
show the presence of sulphuric acid. Acidify the filtrate 
with hydrochloric acid, and boil to expel the carbonic acid. 
When the carbonic acid is all expelled the solution is ready 
for the precipitation of the sulpimric acid with barium- 
chloride solution, and the determination of the barium sul¬ 
phate as before. If the ore contains barium sulphate it 
will remain undecomposed with the precipitate of mixed 
carbonates.” 


1. What is Aaron’s method for the determination of 
sulphur? 

2. In what way is Aaron’s method defective? 

3. What is the best decomposing agent for all ores? 

4. What is the mode of procedure? 

5. After fusion, how would you treat the contents of 
the crucible? 

6. What is added to the filtrate after filtering and 
washing? 

7. What is done if the substance contains silica? 

8. After filtering off the silica, what is the next thing 
to do? 

9- Why are the hot solutions necessary? 

10. After settling and filtering, how is the precipitate 
on the filter treated? 


OF SULPHUR 165 

11. How long is the washing in hot water continued? 

12. What is next done with it? 

13. How is it prepared for ignition? 

14. What is done with the filter? 

15. What is the appearance of the barium-chloride? 

16. After weighing how woifid you determine the 
amount of sulphur, and why would you multiply by 

0.13734? 

17. In what cases can this method be shortened? 


ASSAY OF PLATINUM. 


1. Platinum and gold concentrates are separated froir^ 
the black sand as much as possible and melted with an 
equal weight of pure silver and a little borax to clean 
Place them in a small black lead crucible, pour the charge 
out on an iron plate and treat as an alloy the same as a gold' 
bullion assay. 

2. But it must be parted with sulphuric acid instead oi 
nitric acid, and the cornet should be boiled in the concen¬ 
trated acid for twenty minutes, when the acid is poured olT 
and fresh added, boiling for ten minutes longer. 

3. The resulting cornet is washed, dried, cleaned, an-i 
weighed. 

4. The weight being gold and platinum, some small 
amount of silver invariably remains in the cornet. 

5. So it is necessary to run a proof gold assay made up 
exactly as the regular assay and along with it. Whatever 
gain in weight (above the weight of the gold and platinum 
taken) the proof shows, must be deducted from the weight 
of the cornet obtained in the regular assay. 

6. Alloys Containing Iridium and Osmium.—Alloys 
containing these rare metals will be found with the gold 
and platinum cornet, and may be separated by dissolving 
the cornet in aqua regia, evaporating until the nitric acid 
is expelled, diluting with distilled water, and filtering off 
the iridium and osmium which may be dried and weighed. 

7. We now have a solution containing the gold and. 
platinum dissolved with the aqua regia and nitric acid ex¬ 
pelled. 

8. To separate them we first determine the platinum by 
mixing the solution in a beaker with potassa until the- 




ASSAY OF PLATINUM 


167 

greater part of the acid is neutralized; add potassium chlo¬ 
ride slightly in excess, and then add a pretty large quan¬ 
tity of strong alcohol; if the solution of platinum is very 
dilute, concentrate it by evaporation before adding alcohol. 

9. After twenty-four hours collect the precipitate on a 
rather small filter, wash with alcohol at 80 per cent. Dry 
thoroughly at 100° C. and transfer to a porcelain crucible; 
dissolve the portion which adheres to the filter, and, evap¬ 
orating the solution in the crucible, ignite with hydrogen 
to convert the compound into metallic platinum and potas¬ 
sium chloride. 

10. Reduction is best effected if the heat is very gradu¬ 
ally applied and does not quite fuse the potassium chloride. 

11. After reduction, wash out the potassium chloride, 
ignite and weigh the platinum. 

12 . The filtrate and washings from the platinum is now 
evaporated to a small bulk and hydrochloric acid added, if 
it does not already contain some of that acid in the first 
state, and add a clear solution of ferrous sulphate in ex¬ 
cess; heat gently for a few hours until the precipitated fine 
gold powder has completely subsided; filter, wash, dry and 
ignite. Cool and weigh metallic gold. These results are 
accurate. 


EXERCISES. 

1. How would you fuse platinum and gold sand? 

2. What would you boil the cornet in to part it? 

3. How is the cornet treated after parting? 

4. Of what is it composed? 

5. Would you run another assay? 

6 . How are the iridium and osmium obtained? 

7. Where are the gold and platinum now? 

■8. How is the platinum now separated? 



ASSAY OF PLATINUM 


168 

9. What is the platinum washed with? For what pur¬ 
pose? 

10. How is it reduced? 

11. How are the filtrate and washings now treated to 
obtain the gold? 

12. How, and with what is the gold precipitated? 




COAL ANALYSIS. 


1. An approximate analysis of coal may be made by 
determining the amount of moisture, volatile matter, coke, 
ash, and sulphur; but if the actual amount of carbon, 
hydrogen, and nitrogen is required, an elementary analysis 
must be made which involves much time, labor, and ap¬ 
paratus, but for ordinary purposes an approximate analysis 
will suffice. 

2. To Determine the Moisture.—Weigh out 2 or 2^ 
grammes of the finely powdered coal and place it in a dish 
in a dry oven with thermometer attached. Dry for one 
hour at 105 to no degrees C. and the loss is moisture. 
With the quantity of coal taken the loss of weight appears 
greatest at the end of this time, but upon a further heating 
it actually increases in weight owing to the oxidation of the 
pyrites. 

3. Determination of Volatile Matter.—About 2 to 2 ^ 
grammes of the powdered coal are heated from 4 to 5 min¬ 
utes over a Bunson flame in a platinum crucible with the 
cover on and then immediately, without cooling, for four 
minutes in a hot flame until the crucible and contents are 
at a red heat and all gas has escaped. The loss is set down 
as volatile matter and moisture. The volatile matter car¬ 
ried off one-half of the sulphur. Subtract moisture and 
we have the weight of each; the residue gives coke and ash 
which are now separate. 

4. Determination of the Ash.5—Weigh out one or two 
grammes of the finely powdered coal, place it on the pla¬ 
tinum crucible, cover on a wire gause over a Bunsen’s 
burner; heat gently at first until the moisture and volatile 
matter has passed off, then keep at a led heat until all the 


COAL ANALYSIS 


170 

carbon has burned out, leaving the ash on the cover. The 
weight of the ash subtracted from the weight of the coke 
gives fixed carbon and one-half sulphur. 

5. Determination of Sulphur.—Sulphur in coal exists 
in two forms, as pyrites and as calcium sulphate. 

6. The total amount of sulphur may be determined by 
heating two grammes of the powdered coal in six times its 
weight of pure sodium carbonate or caustic potash in a 
platinum dish, and treated the same as the assay of sulphur 
on page —, and weighed as barium sulphate, and then de¬ 
ducting one-half of its weight from the volatile matter and 
the other half from the fixed carbon. 

7. The means of tabulating results is best illustrated by 


the following example: 

Moisture . 3.2 

Volatile matter X i sulphur.26.5 

Fixed carbon X i sulphur.60.3 

Ash, including phosphorus.lo.o 

Sulphur .0.7 


When the sulphur is determined and one-half deducted 
from the volatile matter and the other half from the fixed 
carbon, the results will stand as follows: 


Per Ct. 

Moisture .3.20 

Volatile matter .26.15 

Fixed carbon . 59-95 

Ash, including phosphorus.10.00 

Sulphur.70 


100.00 

100 parts of the raw coal gave of 
coke.69.95 














COAL ANALYSIS 


The coke was composed of 

Pr Ct. 
Carbon. .85.69 
Ash.14.31 


171 


100.00 including sulphur .0070 per cent, 
including phosphorus—trace. 

It is sometimes necessary to calculate the quantity of 
heat evolved during combustion of a given amount of fuel. 

8. The products of combustion are of two sorts: 

First—The physical products, the heat and light for 
which the combustion is generally produced. 

Second—The mechanical products which are to be con¬ 
veyed away. The heat of combustion is measured in heat 
units, a heat unit being the quantity of heat required to 
raise one gramme of water from 0° to 1°. 

9. Thus the heat of combustion of carbon when burnt 
in oxygen gas in the ordinary physical state, is called the 
calorific power of the combustible, and it has been found 
that burning one gramme of wood charcoal in oxygen 
would heat 8,080 grammes of water from 0° to 
1°. Knowing, therefore, the quantity of carbon in a given 
fuel it is easy to calculate its value for heating purposes by 
multiplying the percentage of carbon obtained in a coal 
by 8,080 will give us the units of heat, but this will always 
be found to be too low, as hydrogen is always present in 
coal, more or less, which is available as fuel, making the 
results too low, and to be accurate an elementary analysis 
must be made. 

EXERCISES. 

1. What is the difference between an elementary and 
an approximate analysis? 

2. How is the moisture in coal determined? 








COAL ANALYSIS 


172 

3. How is the volatile and combustible matter deter¬ 
mined? The coke? 

4. How would you determine the ash? 

5. How is the amount of sulphur determined? 

6. From the above analysis, from what do you find that 
the sulphur must be deducted? 

7. How are the results from the above analysis re¬ 
ported ? 

8. What is a heat unit? 

9. What is meant by the calorific power of coal? 


THE PREPARATION OE PURE GOLD AND 

SILVER. 


Pure gold and silver are necessary in all well regulated 
assay offices for the purpose of making check assays on 
bullion, and while proof gold can be purchased at most of 
the refining works at $40.00 per ounce, it can as well be 
manufactured by the assayer if he has had much experience 
in the business. 

The best material to use is the gold cornet which is 
usually about .998 fine and the other 0.002 parts being sil¬ 
ver, weigh out 1,000 of gold to which add 2^ parts of pure 
silver and from 10 to 12 parts of pure lead; cupel, anneal, 
and roll into a cornet. Boil in C. P. nitric acid of 27 
Baume, for twenty minutes. The acid is poured off and 
the cornet washed several times with distilled water. The 
cornet now consists of gold with a trace of silver. 

The gold is now weighed and placed into Erlenmeyer 
flask and aqua regia added. It will need 4 parts of the acid 
to 1 of the gold, by weight, to dissolve it. The acid is 
added gradually and slowly heated to boiling. When all is 
dissolved the contents are diluted with distilled water and 
allowed to stand for several hours. The clear liquid is now 
decanted off into a large porcelain dish; evaporate until all 
of the nitric acid and most of the hydrochloric acid is ex¬ 
pelled; dilute largely with distilled water and filter through 
a heavy filter paper into a large glass beaker. Do not 
wash the filter, but leave any solid substance behind upon it. 

Heat the filtrate nearly to boiling and add an excess of 
saturated solution of oxalic acid; let it stand in a warm 
place over night, when all the gold will be precipitated, and 
the liquid found colorless. It is then poured off and the 


GOLD AND SILVER 


174 

gold washed several times with warm water, then with 
strong ammonia water to dissolve the last trace of any 
chloride of silver that it may contain; the ammonia is then 
washed out with distilled water, and finally with dilute 
hydrochloric acid, and lastly again with distilled water, 
until the washings are sweet to the taste. It is now dried 
and melted in a clean clay crucible in which some borax 
has been melted to glaze the sides with borax glass. It is 
then cast into a mold which has been smoked for the occa¬ 
sion. This gold is found to be 999.96 fine. 

The following is a later process taken from the Mining 
and Scientific Press, and seems to be equally as good and 
has the advantage of being much shorter: 

“In the preparation of proof gold, after having dissolved 
several ounces of fine gold in nitro-muriatic acid, allow to 
stand several days that any silver chloride present mav set¬ 
tle, filter the solution, then evaporate to crystallization as 
usual. The manner of converting gold from chloride to 
metallic constitutes the difference between this method and 
the old. After diluting copiously with - distilled water, I 
place the solution in a receptacle from which it is allowed 
to pour slowly into a glass jar containing several pieces of 
pure aluminum; the gold is at once converted from chlo¬ 
ride to metallic, a great amount of heat being generated. 
Remove the larger pieces of aluminum, pour off the solu¬ 
tion, washing the gold precipitate several times to remove 
any acid. Then add muriatic acid, and heat to dissolve 
any small particles of aluminum, after which wash well to 
free from acid. Then dry and melt the gold, which should 
be proof, 1,000 fine if proper care has been exercised.” 

Pure silver may be made by precipitating the silver from 
its nitric acid solution by common salt solution and thor¬ 
oughly washing with warm water, adding strips of zinc 
until the chloride all turns dark, becoming cement silver, 




PREPARATION OF PURE SILVER 


175 

then add dilute sulphuric acid to dissolve any traces of zinc 
that may be left in it. Thoroughly wash, dry, and melt 
with two parts of chalk in a clean and covered crucible. 
Or the following process may be equally as good: 

“In the preparation of proof silver, I select silver as free 
as possible from any gold, dissolve in nitric acid and allow 
to stand for several days that any traces of gold may com¬ 
pletely settle; precipitate the silver as chloride, stirring 
well as precipitation takes place, thus causing the silver 
chloride to be finely divided; then pour off the acid solution 
and 'vash the precipitate well with water. 

"I’lace several pieces of aluminum in this chloride of sil¬ 
ver ])recipitate and add sufficient water to cover, then add a 
small amount of muriatic acid to start reaction; in a short 
time the chloride will be converted to metallic silver. Re¬ 
move the larger pieces of aluminum and wash the silver,, 
then add more muriatic acid, and heat to dissolve any small 
particles of aluminum; wash again well till all acid is re¬ 
moved, then dry and melt the silver, which should be 1,000. 
fine.” 


iy6 


TO FREE LEAD EROM SILVER 


TO MAKE PURE LEAD EREE EROM SIVLER. 

Dissolve (sugar) acetate of lead in warm water and place 
in it a strip of zinc; let stand for a few hours. The lead will 
deposit on the zinc (forming the arbor treej; remove the 
lead from the zinc and wash it with water and a little sul¬ 
phuric acid, and last with water. Dry and melt for use. 


PART III. 






PROSPECTING. 


For the past thousand years it has been the first duty of 
the miner to explore the surface of a country for minerals 
and metals. They are not only a necessity, but an actual 
measure of civilization, for it cannot be denied that the 
country which possesses the greatest weight of manufac¬ 
tured metal has attained a corresponding degree of civiliza¬ 
tion and influence in the world; neither can it be perpetuat¬ 
ed without an inexhaustible supply. Remove the metals 
from the world, knowledge and power would at once re¬ 
lapse into barbarism. 

In modern mining the business of a prospector and ex¬ 
plorer is one of the most important and noble industries 
that man can engage m. To be a good prospector is in 
itself a business that requires many qualifications as well 
as much study and practice, and this has been one of my 
principal thoughts in writing this book. 


XOTES OF instruction 


i8o 


NOTES OE INSTRUCTION TO THOSE IN 
SEARCH OF THE PRECIOUS METALS. 

The prospector should observe the character of all loose 
rocks found in ravines and gulches, especially in eddies, 
which are of frequent occurence in mountain districts. In 
searching the sands washed down by the rivers, it is well 
to bear in mind that if the bed of the river which flows 
through a level or open country, yields fine gold dust, it 
will probably yield larger or coarser gold near the moun¬ 
tain, as the finer and lighter particles will float farther 
away. 

Very commonly, in a canyon or gulch where gold is 
found, an accumulation of boulders or gravel may be no¬ 
ticed high up on the sides of the range, and more or less 
parallel to the bed of the creek. Portions of such de])osits 
should be carefully examined by washing in a pan, as the 
gold-bearing matter, whether carried there in past ages by 
running water or glaciers, may contain gold in rich lavers, 
called by miners the rim-rock, which is always a riffle for 
the deposit of gold. 

Should there be several distinct deposits the lower stra¬ 
tum on the bed-rock would be the richest. It is advisable 
to remember that when gold is found in placers or hill¬ 
sides, the chances are that gold veins traverse the neigh¬ 
boring elevations of land. Such elevations may prove 
profitable to work, but this is not necessarily the case. 

Almost all the rich metal bearing gold veins are found 
chiefly in the rocks of an older date than those of the coal 
measures, although some in California are found in a more 


NOTES OF INSTRUCTION 


i8i 


recent formation, and the famous Comstock lode was, no 
doubt, formed by the hot alkaline waters as late as the 
tertiary period. Without entering into a discussion as to 
the formation or origin of quartz veins, I will say that the 
same law applying to veins in one district also applies to 
another as to their compass bearing. Consequently they 
are parallel, although some distance may separate one lode 
from the other. 

In some mining districts the second series of veins run 
at right angles to the first and principal. Such lodes are 
either of a dif¥erent nature of mineral to that of the first, or,, 
if the same, are very poor in quality. 

It is well, also, to remember that a true mineral vein is 
not likely to exist algne; but many more, either richer or 
poorer, may be found to form a mineral belt. For this 
reason the prospector should not set his affections upon one 
vein alone until he has examined the whole district to his 
entire satisfaction. In searching for veins, he should study 
the general geological formation of the country, the cutting 
landslides, the cliffs, the sides of valleys, the sections of 
banks exposed to view by the action of water, river beds, 
and dry channels, and if he fails to find samples of rich 
float-rock he should travel on as long as he can find sim¬ 
ilar rock. When no more is found he should then start up 
the hillside or mountain to discover the parent rock from 
which they came. Very frequently at the base of the hill 
or mountain there is a deposit in the soil washed down from 
more elevated ground. High up on the hill may be found 
the float-rock in the form of 1 )Oulders, or detached por¬ 
tions of the vein, which would not be far from the ore in 
the place. 

By taking notice, however, of the various undulations 
and drift, the prospector may come across outcrop on the 
steep side of the gully, or backbone of the ridges; and. 


i82 notes of instruction 

failing in this, he may travel toward the summit of any 
range of hills to find the vein. 

Fluor spar (fluate of lime) is favorable for lead and cop¬ 
per; calc spar for lead and silver; but many other valuable 
minerals may be looked for in gulches and ravines, such as 
stream tin, antimonial silver, metallic copper, platinum 
grains, and telluride of gold; or he may travel across a sec¬ 
tion of the country where the strata are tilted and folded 
and metamorphosed, and the edges of a stratum for a con¬ 
siderable distance are upturned, so removing all doubts of 
its identity. Each section shows the strata as they succeed 
each other, and it supposes a cutting of them in the same 
manner that by cutting an onion we see the different coats 
of which it is composed. 

\ 

All sections, when the contrary is not expressed, are sup¬ 
posed to be made perpendicular to a horizontal plane. In 
a plane, we lay down on a horizontal plane, the superficial 
area occupied by each bed as it rises to the surface, or, in 
the language of miners, bassets or crops-out. 

We trace or delineate the superficial edges of strata by 
traveling across their basset edges, in a number of parallel 
lines, noting on a map made on a piece of paper, the sev¬ 
eral points at which we pass from one kind of rock to an¬ 
other. 

Thus, in the annexed diagram, in crossing the country 
intended to be represented by it in the line A B, A being 
supposed to be situated on sandstone, we should pass at a 
from sandstone to limestone, at b from limestone to slate, 
at c from slate to granite, at d from granite to slate again, 
at e from slate to limestone, at f from limestone to sand¬ 
stone again; and in traveling the same district along the 
lines C D and E F, we should find these changes take place 
at the points a, b, c, d, e, f, and a, b, c, d, e, f, respectively. 


NOTES OF INSTRUCTION 


183; 



In this way the miner can construct a geological man of 
the country over which he may prospect, and fully deter¬ 
mine its nature and mineral character. 

For the gold-bearing vein there is none so good as the 
one which has an iron cap. The iron oxide is really the 
result of the decomposition of iron pyrites and the pyrites 
would be found deeper down after finding the vein. The 
prospector may dig a trench at right angles, if possible, to 
the lode, in order to examine its character, the nature of the 
ore and the gangue, and to find the boundary wall, viz., the 
upper and hanging wall, and the lower or footwall, as well 
as to note the direction or strike of the lode. He must 
sink a prospecting shaft a few feet deeper than the bottom 

of the trench to determine the exact body of the ore, as the 
lode may be distorted from its original shape near the sur¬ 
face. But when the direction of the lode is once ascer¬ 
tained, other pits, lower down, or higher up the hill, should 
be made so as to test the continuity of the vein. Should 
the vein prove continuous, and the surface assays turn out 
well, development may begin. 

At the same time no person should be led away by the- 

































NOTES OF INSTRUCTION 


184 

hope that ti.e deeper the vein the richer the ore. While 
it is a fact that lead and copper veins do improve by depth, 
and many gold veins have also, yet very many do deterior¬ 
ate in value as they go down. But it is a recognized fact 
that veins vary in quality and nature, according to the 
strata through which they pass, and there are chances that 
the vein may ‘‘pinch out,” or end in a “pocket,” or become 
changed in character and value when least expected, and 
it is well to err on the safe side and never take your ore to 
an incompetent assayer to be tested, for many of the best 
assayers are often troubled to get the proper dressing in 
assaying-sulphurets, arsenical, or zinc ores. While the 
capitalist may risk his money in the chances he may take, 
the prospector’s time and labor are worth too much to ad¬ 
mit of his expending endless labor in obtaining experience 
in development work or on uncertain and unreliable as¬ 
says. 

If the lode carries gold or silver or other valuable metal, 
that fact is not enough to depend upon in estimating its 
worth. Often the gold is in very fine powder, invisible to 
the eye, or perhaps coated with a rusty film of silica, which 
would prevent amalgamation, and, in consequence, though 
the assay may be favorable, the extraction of the gold from 
the ore by amalgamation is not satisfactory, as the mercury 
may “sicken” or “flower.” Again, the ore body may be 
rich enough, but much depends upon the nature of the 
other constituents. Antimony or arsenic may render it 
valueless. Before digging commences several samples of 
the rock should be taken from the lode and examined by 
an expert and reliable assayer, and the facts ascertained as 
to the value and quality of the ore, the best methods of 
treating it, etc. Unfortunately, this is not convenient in an 
out-of-the-way place. To assay correctly means a course 
of training. For this reason no one should undertake the 


XOTES OF INSTRUCTION 


185 


business unless he has practiced under the instruction of a 
competent assayer. Still, there is no reason why an inex¬ 
perienced person should not attempt to qualitatively test 
minerals by some simple methods. To be compelled to 
go to a chemist, geologist, or mineralogist for every little 
matter of inquiry is not only inconvenient, but trouble¬ 
some, as there are so many unreliable, so-called authorities 
to be met with. 

Because some miner pronounces such a mineral to be 
unlike something he has seen in Cornwall or California, or 
some other place devoid of metal, the prospector need not 
be too ready to accept such an opinion, for, as a rule, the 
ordinary miner may be an expert in certain matters, like 
running a drift, timbering a tunnel, etc., but still may have 
erroneous notions about such minerals as gray copper ore, 
silver glance, fine or coarse grain galena, etc. The most 
experienced mineralogist cannot, for a certainty, tell at first 
sight, how much gold or silver may be in a particular rock. 
These metals are sometimes found in the most unlikely 
formations, and it is quite common to find a handsome, 
good-looking specimen which will disappoint everybody 
and carry nothing at all. Many of the silicates and car¬ 
bonates and chlorides are perfectly unmetallic to look at, 
yet have been found very rich. For a long time the chlo¬ 
ride of silver deposits in Colorado were passed over with¬ 
out being noticed, as was also the case with the carbonate 
of lead in Leadville, which, after discovery, in five years, 
converted Leadville into a city of 30,000 inhabitants. 

After the prospector has discovered his vein of ore he 
must consider, before he thinks his fortune made, how far 
distant are fuel and water for successful operation. He 
must not grudge a little money in having a dozen or more 
of his samples assayed, and obtaining the advice of a proper 
assayer. He must lemember that a iow-grade ore in one 


NOTES OF INSTRUCTION 


186 

place is worth more than a rich one in another, and much 
more depends upon the character of the ore, whether it 
must be treated or not. 

Another great mistake many miners and prosepctors 
make is in distributing their samples of ore from a mine 
among so many different assayers, in that the more assays 
a man makes from one mine, the better acquainted he be¬ 
comes with the ore, the method of treating it, and the 
fluxes necessary to obtain the required results. 

I have known some first-class assayers, who, being un¬ 
acquainted with the ore, and not taking time to make a pre¬ 
liminary assay to determine its real character, make returns 
on a sample of steatite and quartz rock of only $12.00 per 
ton, when in fact it was really worth $25.00 or $30.00 per 
ton. 

The miner should select the best assayer he knows of and 
stay with him, and not spend his time going around tell¬ 
ing how such an assayer got more to the ton out of the 
same kind of rock from the same vein than some other 
assayer did. Such men are only exposing their ignorance 
among old mining men who know that gold is never equal¬ 
ly distributed in a quartz vein, and that it is rarely, if ever, 
possible to get two assays to go alike even from the same 
pulp after sampling, and that the only reliable knowledge 
of the value of a mine can be obtained from the average of 
a large number of assays from it. 

Nearly all the great mines have been found in the man¬ 
ner which I have described, and were rich to start with; if 
not, it is of but little use to dig in the earth to find a mint. 

It is a well-known fact that all mountain regions where 
uplifts and foldings of strata and metamorphism have taken 
place, are favorable to the metal-bearing veins. 

As for the geology of the country, much might be said, 
and much valuable information attained by miners and 


NOTES OF INSTRUCTION 


187 

prospectors in their search for the precious metals; and 
their observations extended and generalized have given us 
a large amount of knowledge as to the structure of the 
earth. The depth, however, to which this structure is laid 
open by the hand of man, is extremely limited; the deepest 
mine in the world penetrates little more than half a mile. 

The convolutions which the earth has undergone has ex¬ 
posed its structure to a much greater depth. In cliffs, on 
the sides of ravines, on the banks of rivers, and on the sea¬ 
shores, the strata may frequently be seen resting upon one 
another in an inclined position, their original state having 
been disturbed by a force acting from below. 

These natural sections often extend for many miles, and 
the inclination of the beds causes them to emerge succes¬ 
sively to the surface, and enables us to estimate the thick¬ 
ness of the whole series of beds. 

These beds may have been thrown up and pierced by 
volcanic rocks of the granite type, in large masses forming 
the axes of greater mountain ranges, as the Sierra and Col¬ 
orado ranges, appearing in the midst of stratified rocks like 
islands in the midst of the sea. 

These plutonic rocks in many places may never have 
penetrated the strata, but merely raised and folded them 
and afterwards have been sculptured and worn away as 
above described. 

Fissures, passing through many strata and many forma¬ 
tions, are produced by shrinkage in the earth’s crust, and 
are, therefore, often many miles in length and many feet in 
width and pass downward to unknown depth. Evidently 
the cause of great fissures is the usual folding or wrinkling 
of the crust of the earth produced by the contraction of the 
interior portion. The natural tendency of such folding 
would be to form a parallel system of fissures in the direc¬ 
tion of trie folds, and so at right angles to the folding force 





NOTES OF INSTRUCTION 


188 

Fissures are thus found in systems parallel among them¬ 
selves and at the axes of the mountain chains. 

Heat is a necessary agent in forming a quartz vein as 
well as changing the nature of the abounding rock from a 
crystalline structure to a metamorphose condition. Thus 
hundreds of miles of rock are universally changed. The 
only theory by which the formation of a quartz vein can be 
established is by the hot alkaline solutions highly charged 
with silica. This is plainly evident from the material of 
the vein itself. The ribbon structure and the interlocked 
crystals suggest at once successive deposits from solution, 
especially as a similar structure occurs in filling all kinds 
of cavities which could not have been filled in any other 
wav. 

Quartz is the most common of all vein matter. There 
are two varieties of silica, one having a specific gravity of 
2.2, the other 2.6; the former is quartz glass, the latter is 
the true quartz, and cannot l)e formed except by the humid 
way, and has always been produced by slow deposition 
from solution, and the specific gravity is always 2.6. The 
"beautiful crystals of the former often found could be formed 
only by crystallization at a low temperature, as they will 
not stand fusion. 

Fissures running deep into the interior of the earth could 
not remain free from water, and must necessarily be highly 
heated, and it has been determined that there must be a 
temperature of between 200 and 350 degrees, centigrade, 
which would dissolve almost any substance. These heated 
waters are strongly alkaline carbonates and alkaline sul¬ 
phides which are the only solvents for quartz. An abun¬ 
dance of these springs now exist all over the country, but 
are now much cooler than formerly, although still deposit¬ 
ing silica (quartz) and carbonates of lime, cinnabar and 
iron. All these metals found in quartz veins must have 


NOTES OF INSTRUCTION 


189 

been deposited l)y the same solutions that deposited the 
quartz. The metallic sulphides are the most common form 
of ore, and they come in contact with the hot solutions of 
the alkaline carbonates, meeting and coming together in 
the same fissure with other waters containing metallic sul¬ 
phides which would precipitate the metals. These iron 
sulphates come from the oxidation of sulphides, and the 
sulphides from the deoxidation of the sulphates. This is 
•only an example of the perpetual cycle of change. 

* '‘Again, the gold in the vein is leached from the 
strata which received it from the sea; but again, doubtless, 
the sea received it from the rocks, and this brings us to an¬ 
other perpetual cycle of change. In the strata the quantity 
of gold is so small as not to be detected, but yet abundant 
enough to furnish all the gold in existence. From thence 
it is carried and concentrated in the vein in a still more 
available form; following the disintegration of the vein it is 
carried down by the currents along with other material, 
neatly sorted out and deposited in the placers in a yet more 
available form.” 


*Le Conte. 







Lode Worked by Vertical Shaft. 

1 , Lode. 2, Sliaft, 15—120 fathoms cross-cuts. 
Productive Strata. 4, Unproductive Strata 
5, Adit Level. 6, Dressing Sheds. 


3 . 
























SYNOPSIS OF SOME OF THE RARER AND LESS 
WELL-KNOWN METALS. 


1. GOLD is generally supposed to be the most valuable 
of metals, but this is a mistake; for, while it may be one of 
the oldest metals known, it is far from being the most prec¬ 
ious. Its discovery is shrouded in the darkness of the 
early ages, and it is the only metal of a yellow color. It is 
frequently alluded to in the Old Testament; the Jews re¬ 
fined it by cupellation, a process which has never been im¬ 
proved upon. Jewelry and vessels of it have been found in 
Egyptian tombs, which afford evidence of its use before the 
government of Joseph. Pliny speaks of separating it by 
amalgamation with mercury. 

The United States government places a valuation of 
$20.67.18 per ounce or about $250.00 per pound. 

2. SILVER.—The discovery of silver appears to have 

been coeval with that of gold, and dates back to the earliest 
times of the world’s history. In the book of Genesis we 
learn that silver was current money with the merchants, 
about 2000 years before - the Christian era, and frequent 
mention is made of this metal in the subsequent books of 
the Bible. The metal is always found alloyed with gold, 
and gold with silver. Evidently nature intended bimetal- 
ism. Silver is worth, at the present time, about $12.00 a 
pound. f f 

3. PLATINUM. — The metals platinum, palladium, 
rhodium, iridium, ruthenium, and Osmium are united in a 



192 


RARER METALS 


family by a striking similarity in chemical character and by 
their association in natural occurrences. 

4. A rather rare ore, called platinum ore, or polyxene, 
is almost the only native material which is available for their 
extraction; it contains them all in the reguline form. The 
metal platinum is an exceedingly useful metal, very ductile 
and malleable; two pieces of the metal can be welded to¬ 
gether at a white heat, and it requires the oxyhydrogen 
flame to melt it. Its value is about $130.00 per pound. 

5. NICKEL. The metal is obtained chiefly from nick- 
eliferous iron pyrites (magnetic variety) which only con¬ 
tains the element as an accessory constituent. The native 
arsenides, an impure regulus (called speiss) formed in the 
preparation of smalt, are the other sources of the nickel ''1 
commerce. Metallic nickel Sp. Gr. 8.82, has a silver-white 
color, brilliant metalic lustre, and does not tarnish when 
exposed to the atmosphere. Its value is about 60 cents per 
pound. 

6. ALLUMINUM is readily obtained by reducing 
either the chloride or the native fluroide (cryolite) with me¬ 
tallic sodium. It has a brilliant white lustre, and possesses to 
a high degree all the qualities of a useful metal. It has a low 
Sp. Gr. of 2.56 and a very great tenacity, and its value is 
from 50 cents to $2.00 per Troy pound. 

These values sink into insignificance in comparison to the 
value placed upon some of the less known metals, owing to 
the cost of separating them froth their ores. 

7. BARIUM.—This metal decomposes cold water with 
the evolution of hydrogen. 

8. But less readily than the alkaline metals. Barium 
salts communicate an apple-green color to the blowpipe 
flame. Strontium salt gives a brilliant crimson color, and 
calcium salt an orange-red color to the flame. The metal 
barium sells for $950.00 a pound. 


RARER METALS 


193 

9. CALCIUM is a yellow metal of the color of gold, 
largely alloyed with silver. In hardness it is intermediate 
between lead and gold, and is very ductile, and melts at a 
red heat. It is worth $1800 a pound. 

10. CHROMIUM.—This metal is extracted from the 
ore chromate of iron, a massive and compact granular, 
crystaline black-colored mineral Sp. Gr. 4.4, and hardness 

5.5. It occurs usually in serpentine. The metal is worth 
about $200 per pound. 

11. CERIUM, LANTHANUM, AND DIDYMIUM. 
These three rare elements are found inseparably united in 
serite, allanite, lanthanite, yttrocerite, parasite, and several 
other very rare minerals. In regard to the elementary sub¬ 
stances but little is known. Cerium, which has been ob¬ 
tained by reducing its chloride with sodium, is a soft metal 

like lead. When polished it exhibits a high metalic lustre 

« 

and its Sp. Gr. is about 5.5 and worth $160 per ounce or 
$1920 per pound. 

12. DIDYMIUM was isolated by Masander and is 
worth about $1800 a pound. 

13. CALUMBIUM (Niobium).—This element forms 
the acid radical of calumbite, samarskite, euxenite and a 
few other rare minerals, with various metallic oxides. It has 
a black color, a submetallic lustre and a Sp. Gr. from 54 to 

6.5. When finely powdered it is easily decomposed by fus¬ 
ion with potassic bisulphate. 

14. The metal calumbium is a black powder. An infu¬ 
sion of nut-gall gives, with acid solutions containing calum¬ 
bium, a deep orange-red precipitate. It is valued at $120 
per ounce. 

15. GLUCINUAI.—A metallic element found in Beryl. 
The metal is very light (Sp. Gr, 2.1), is malleable, has a 
bright white lustre, does not alter in the air, even when 




Rx\RER ME PALS 

heated. It reseml)les aluminum, and is worth $250 per 
ounce, when sold. 

16. GALLIIAI.—This metal was discovered by means 
of the spectroscope in zinc blend. 

17. The metal is bluish and has the remarkable property 
of fusing' at 30.1 degrees. The molten metal resembles mer¬ 
cury and remains liquid for several weeks even at 0°. If, 
however, the glo1)ule is touched with a small fragment of 
the solid metal, it at once crystallizes. Rut, although so fusi¬ 
ble, gallium is not volatile at a red-heat. The Sp. Gr. of 
the metal is 5.9. It is worth $3,250 an ounce and is rarest 
and most precious of all known metals. 

18. INDIUM.—This metal is another associate of zinc 
found in blend, and, like gallium, was discovered with the 
spectroscope. It takes its name from well-marked indigo- 
blue bands which its flame shows when examined with this 
instrument. The metal is softer than lead. Sp. Gr. y.42. 
It has a white metallic lustre, which it retains in the air. 
The best solvent is nitric acid. 

19. Heated on charcoal before the blowpipe, it colors 
the dame blue and gives an incrustation of the oxide. 

20. IRIDIL M is a very hard, white, brittle metal and 
found in the black sands in gold washings. Sp. Gr. 21.15. 
The pure metal is not acted on by any acid; but, when al¬ 
loyed with platinum, it dissolves in agua regia. It may be 
rendered soluble by fusion with alkaline reagents. Its value - 
is $658 a pound. 

21. LITHILAI, RURIDIUM AND CAESIUM are 
found in minute (juantities in certain mineral water, in lepi- 
dalite mica and in a few other rare minerals. They are al¬ 
ways associated with potassium and sodium, to which they 
are closely allied in their chemical relations. The metal 
lithium is remarkable as being the lightest solid known. 
Its S]). Gr.—0.59; its value is $160 per ounce. 


RARER METALS 


195 

22. OSSMIUM.—In the most compact condition in 
which this metal has been obtained it has an Sp. Gr. of 21.4 
and a bluish color much like zinc. It has never been fused, 
but it slowly volatilizes at the temperature at which ruth¬ 
enium and iridium melt. W hen in powder, ossmium is 
very combustible. It will take fire at the melting point of 
zinc. It is one of the most poisonous substances known. 
Its value is $640 a pound. 

23. PALLAJJAIUM is a brilliant white metal, resem¬ 
bles platinum more closely than either of its associates, al¬ 
though best known as a subordinate constituent of platinum 
ore. It is harder than platinum, has less tenacity and is not 
so ductile. Nevertheless it can be wrought with facility. 
The quantity of hydrogen '‘acculated” by palladium 
amounts to nearly one equivalent of the metal and produces 
a marked change in its physical qualities. From these facts 
Professor Graham inferred that the metal charged with gas 
is an alloy of palladium and metallic hydrogen, which he 
called hydrogenium. Its value has not been determined, 
to my knowledge. 

24. TANTALUM is associated with calumbium in the 
native calumbates. The chief constituent is Tantalite, 
which has a higher Sp. Gr. than calumbite, which varies 
from 7 to 8. By reducing sodio-tantalic fluride with sodium 
a black powder is obtained, which is metallic tantalum, and 
worth $144 per ounce. 

25. TELLURIUM is closely allied to Selenium, and 
both closely allied to sulphur. Selenium, in its elementary 
state, is a brittle solid, having a glossy fracture and a brown 
color, Sp. Gr. 4.3. But in tellurium we find a more marked 
difference. The elementary substance is a silver-white 
color, a bright metallic lustre and apparently a metal. Its 
Sp. Gr. equals 6.2: its value is $9 an ounce. 

26. THORIUM.—The mineral thorite, an orangite, is a 


RARER METALS 


196 

hydrous silicate of this rare metallic element, which has 
been found as a subordinate constituent in euxenite, mona- 
zite, gadolinite and orthite. The unhydrous oxide is a 
white powder which glows when heated and becomes more 
dense. The chloride may be reduced by sodium, and the 
metal may be thus obtained as a gray lustrous powder 
which readily burns in the air. Its value is $272 per ounce. 

27. 'hHALLIUM is a very rare element found in varie¬ 
ties of pyrites and crookesite. A selenide of copper and 
thallium form a copper mine in Sweden. Rut thallium has 
not as yet been isolated as a metal, to my knowledge. 

28. \'AXADIl"M was discovered in 1830 in the iron 
ores of Sweden. It has Ireen found associated with lead 
and copper and termed the vanadates of these metals. It 
resembles the native phosphates and arsenates. ()xides of 
vanadium are a brown crust formed by prolonged exposure 
of metallic vanadium to the air and looks much like metallic 
copper. It is found to be quite extensive near Earmington, 
in Washington. The metallic powder has a Sp. Gr. equal 
5.5 Its value is $320 per ounce. 

29. YETTRIIAI. ERBIUM and their associates.— 
These rare minerals, gadalinite, euxenite, keilhanite, and 
lamarskite, contain a mixture of earths which quite closeh'v 
resemble glucina. \ erv little of these elements is yet 
known; but several able chemists are investigating the sub¬ 
ject and no doubt soon we will have more definite informa¬ 
tion regarding them. Yettrium is said to be worth $144 
per ounce. 

30. ZI RCON I L^M.—The powder metal burns rapidly 
in air. The crystalline metal requires to be heated in an 
oxyhydrogen fiame, if it is to catch fire. Its Sp. G. is 4.15. 
When heated to whiteness it remains unfused, and radiates 
an abundance of white light. This property has been util¬ 
ized for the construction of a new kind of gaslamp, in which 


RARER METALS 


197 

a colorless flame, produced by the combustion of a mixture 
of gas and air, serves to heat a hollow cylinder of zirconia 
suspended over it by means of a platinum gause. Its value 
is $250 per ounce. 

Many other metals have also been discovered, but no 
value can be placed upon them, as they have yet found no 
commercial value, but no doubt in the future the list will be 
greatly increased. The analysis of these ores belongs to the 
chemist, and not to the average asayer, and the synopsis of 
them is merely inserted here for information, as I have 
often been called upon for information .concerning them. 

(1) What can you say of (iold? Its origin, its use in 
the arts and coins; its purity and allies, and Sp. Gr.? 

(2) What can you say of Silver? Its history, purity, and 
the kind of ores in which it is found; and natural allies, and 
its Sp. Gr.? 

(3) W'hat are the native associate s of Platinum ore? 
What is the name of the ore, and its Sp. Gr.? 

(4) What is the character of Platinum as a metal, and 
how can it be melted? What is its value and Sp. Gr.? 

(5) From what ores is Nickle found, and what is its 
native ally? 

(6) How is Alluminum obtained? What is the char¬ 
acter of the metal, and its Sp. Gr.? 

(7) What is the color of the B. P. Flame of Barium 
Salts, and how will you distinguish it from Strontian? 

(8) What is its action on water, and what is its value? 

(9) What is the color of the metal Calcium? At what 
does it melt; and what is the character of the metal, and its 
value? 

$ 

(10) From what kind of ore is the metal Chromium ex¬ 
tracted? What is its use and value, and Sp. Gr.? 

(11) What kind of ores are Cerium and Lanthanum 
found in? How is Cerium obtained from the ores? What 


198 RARER METALS 

is the character of the metal? Its value and Sp. Gr.? 

(12) What can you say of Didymium? 

(13) What is the character of the metal Columbium?' 
How is it obtained from the ore, and what kind of ores? 

(14) What is the test of Columbium in an acid Solution? 
What is its Sp. Gr., and its value? 

(15) From what kind of ore is Glucium obtained? 
What character is the metal? What metal does it resemble? 
And what is its value? 

(16) How was the metal Gallium discovered, and in 
what ores is it found? 

(17) What is the color of the metal Gallium? What is 
its character, its fusing point? What is its Sp. Gr., and its 
value? 

(18) What ores is Indium found in? What is the char¬ 
acter of the metal and its Sp. Gr.? 

(20) What is its flame color, and how is Indium ob¬ 
tained? What is its Sp. Gr.? How is it made Soluble, and 
what is its value? 

(21) In what ores is Lithium, Rubidium and Caesium 
found? What is the Sp. Gr., of Lithium, and its value? 

(22) What is the Sp. Gr. of Ossmium? What is the color 
of the metal, its character and value? 

(23) What kind of metal is Palladium? What is its 
character, and what does it combine with? 

(24) What is Tantalum associated with, and how is it 
obtained from the ore? What character is the metal? What 
is its Sp. Gr., and value? 

(25) From what mineral is Thorium obtained? What 

% 

is the appearance of the metal, and how is it reduced? 

(26) What kind of ores is Thallium found in? 

(27) When was Vanadium discovered? 

(27) When was Vanadium discovered? What is it asso- 


RARER METALS 199 

•ciated with? Where is it found in this country? What is 
its Sp. Gr., and value? 

(28) What kind of ores are yettrium found in, and what 

is known of it? , 

(29) Describe the ore of Zirconium? What is its Sp. 
•Gr.? What is its use and value? 


I 



200 


EXAMINATION OF ORES 


PRELIMINARY EXAMINATION OF ORES. 

All minerals and substances submitted to the assayer for 
analysis should first undergo a preliminary examination to 
determine the character and mineral constituents, thereby 
showing what is the best method of treatment, and, in 
making out his report to his patron, he should briefly in¬ 
form him of these facts as well as the results of his assay. 

Sometimes this preliminary examination is unnecessary 
when an ore is submitted with a statement of its character 
and the constituents required to be determined. Where 
the ore is in a lump form, the assayer, if he is competent, 
can at once determine its chief constituents by an eye ex¬ 
amination, but for practical use and experiment, I here¬ 
with give a few tests of the most common ores, by both the 
wet and the dry method. 

The ore to be tested should be first ground to a fine 
powder in an iron or steel mortar, although in some cases 
the original rock will do. 

ALUMINA.—The metal is never found in the native 
state, but in combination with silica and corundum. Sap¬ 
phire and ruby are nearly pure alumina; emery is an im¬ 
pure alumina: beauxite is a red hydro-silicate of alumina. 
It may well be detected, when dry, by applying it to the tip 
of the tongue and suddenly withdrawing it. If alumina be 
present, it will reveal its desire for moisture by adhering 
to the tongue. Before the blowpipe, when moistened with 
nitrate of cobalt, it will give a clear, blue color to the flame. 
Take a little of the powdered alumina and dissolve it in 
nitric acid by warming, then filter it, and you have a clear 
liquid. Add a little ammonia to neutralize it, which will 


EXAMINATION OF ORES 201 

give a gelatinous precipitate of alumina hydrate, insoluble 
in excess. 

CARBONATE ORE. — Place a drop of strong acid 
upon the rock. If it effervesces or boils up, it contains car¬ 
bonate. Place some of the powdered ore in a test tube 
with acid, and hold over it a glass rod previously dipped 
in lime-water; the drop on the rod will turn milky, showing 
formation of carbonate of lime. It is easily precipitated 
with oxalate of ammonia, but insoluble in acetic acid. It 
gives a white precipitate with dilute sulphuric acid, and is 
soluble in strong sulphuric acid. 

TELLURIUM.—It is found native, also combined with 
gold, silver, lead, and antimony. To test the ore, take a 
small piece and place it on any white piece of crockery— 
a broken plate will do—and heat it with the blowpipe flame 
for a few minutes; now place a drop of strong sulphuric 
acid on the dish, and let it slide down to the heated frag¬ 
ment. As soon as it touches the ore, a beautiful carmine 
color is visible, and when cold the color will fade. 

TELLURIDES IN GOLD ORES.—Heat the pow¬ 
dered mineral in a test tube with charcoal, carbonate of 
soda, and hot water. If telluride be present, it is known 
by the solutions being purplish red in color; boiling in 
sulphuric acid affords a pinkish solution. 

TIN ORE.—There are two kinds of tin ore—oxide and 
sulphide. It may be suspected by-its specific gravity which 
is 4.3 to 7.T The oxide is the heaviest. In color, it varies 
from an almost white to a dark brown, and through all the 
shades of rosin. It may be distinguished from iron by be¬ 
ing soluble in aqua regia. With borax and carbonate of 
soda on charcoal, it will give you a globule of tin. For a 
good test, it is best to mix some of the powdered ore with 
twice its weight of cyanide of potassium in a crucible, and 
fuse it in a forge, when a button of tin will be obtained. 


202 


EXAMINATION OF ORES 

SULPHUR—Melts with soda on charcoal. Moistened 
and placed on a silver coin, a dark stain indicates sulphur, 
but if selenium be present it will do the same. To distin¬ 
guish them, heat some of the powder to redness in the 
scorifier; if it does not smell like a burning match the sul¬ 
phur is not in the form of a reducer. 

SULPHATES.—To some of the powdered rock add 
nitric acid; warm, and filter. Divide the filtrate into two 
test tubes. To one add a solution of chloride of barium. 
If lead be present add nitrate of barium to the other. After 
standing a while, a white, cloudy precipitate shows sul¬ 
phates to be present. 

ZINC.—Sulphide of zinc dissolves readily in dilute solu¬ 
tions of hydrochloric acid and sulphuric acid with evolution 
of hydrogen gas. Before the blowpipe on charcoal it 
leaves a white oxide of zinc, which is white when hot and 
yellow when cold. With chloride of zinc, if you add salt, 
then cobalt, it gives a green-colored mass. Throwing some 
of the ore into the fire will give a brilliant white flame. 

MANGANESE—Disolved in nitric or hydrochloric 
acid gives a faint pink color. Filter it off, and to the filtrate 
add sulphide of ammonia. It will then give a flesh-colored 
precipitate off the sulphide of manganese. Before the 
blowpipe, compounds of manganese color the borax bead 
amethyst in the oxidizing flame. If manganese be fused 
with alkalies, it will give a green manganate color, but the 
solution in all cases will be pink or flesh-color when an 
acid is added to it. 

IRON ORE.—Dissolve the powder with nitric or hydro¬ 
chloric acid, filter, then dilute with water and divide into 
three test tubes. To one, add a drop of sulpho-cyanide of* 
potassium and a blood-red coloration takes place. To an¬ 
other add a little ammonia water and a reddish-brown 
gelatinous mass forms. To the third, add a little of a solu- 


EXAMINATION OF ORES 


203 

Tion of yellow prussiate of potash; a blue precipitate will 
occur. This proves conclusively the presence of iron com¬ 
pounds. 

COPPER ORE.—This will soon dissolve in nitric acid, 
but very slowly in hydrochloric acid. All copper carbon¬ 
ates are either blue or green. The blue copper is azurite, 
but the green is malachite. They are both carbonate ores. 
When dissolved in nitric acid, add ammonia water, and it 
will turn an intense blue color; or place in a dilute solution 
of copper a little yellow prussiate of potash, and it will give 
a mahogany-colored precipitate; or place in a dilute solu¬ 
tion a piece of bright iron, and it will be coated with cop¬ 
per. If it were nickel ore, the green, as it came from the 
acid, would be an apple-green, and would give a precipitate 
with ammonia. With the blowpipe, as a conclusive test, it 
will color the borax bead green when hot. Moisten the 
powdered ore with salt brine, and throw into the fire; an 
intensely blue flame will be seen. 

ANTIMONY.—Is scarcely attacked by either nitric or 
hydrochloric acid, but will readily dissolve in both when 
mixed together (three parts of hydrochloric to one of nitric- 
aqua regia); then add water, which will precipitate a base 
of chloride of antimony. With the blowpipe, it is distin¬ 
guished by its extreme fusibility and vapor. In the candle 
flame, it gives off a white coat on charcoal, extending a 
long way and easily driven about by the flame. Globules, 
if obtained, thrown on a table, while hot, roll along giving- 
off dense white fumes. 

NICKLE ORE.—It is very hard to distinguish it unless 
in the hands of a competent assayer. The pale green oxide 
is (garatite, zaratite or genthite) copper nickel combined 
with copper; another is arsenical nickel combined with 
arsenic. It will dissolve in nitric acid; will give a pale- 
green oxide when filtered from its acid solution; will give a 


204 


EXAMINATION OF ORES 


pale-green precipitate with yellow prussiate of potash. The 
copper nickel is pale copper-red, but it has to be purified 
from other metals before any satisfactory test can be made 
of it. It may be somewhat indicated by the blowpipe on 
charcoal. The borax bead will be bine if cobalt predomin¬ 
ates, and brown if nickel predominates, as they are most 
always associated together. 

LEAD ORGALENA ORES.—Drop a little nitric acid 
on the ore, then add a little water, then a crystal of iodide 
of potassium; a bright yellow precipitate will at once fo: m, 
which shows lead to be in the ore. These tests can all be 
shown with the filtered solution in the test tube if dissolved 
in acid. The chromate of potash gives a precipitate of lead 
which is yellow chromate of lead. Add salt to the solution 
with nitric acid, you have a granular precipitate. 

SILVER ORE.—Boil the powdered ore and filter it. 
Drop into it a little salt water or hydrochloric acid; it forms 
chloride of silver; a white curdy precipitate of the chloride 
of silver is thrown down. This is a good test for all silver 
ore, except the chloride ores. This kind of ores, pow¬ 
dered, should be placed in a test tube with strong ammonia 
water, and corked, being allowed to stand for a few hours. 
Then add nitric acid in slight excess, then salt water, and 
the chloride of silver will soon fall down forming a mi'ky 
white precipitate. Boil the powdered ore in a glass flask 
with a strip of clean copper, bluestone, and salt water. 
This will give a white coat on the copper. 

TEST FOR GOLD BY WET METHOD.—The pow¬ 
dered ore must be boiled a little while in aqua regia (3 parts 
of hydrochloric and i part of nitric acid). A purple pi'e- 
cipitate will be found when proto-chloride of tin is added to 
the solution, which is purple of cassius. 

GOLD.—The best test of gold is the fire assay. When 
an assay office is not convenient, the best way is to grind 




EXAMINATION OF ORES 


205 

the rock to a fine powder, add a little potash, put it into a 
saucer or a small pan or dish of any kind, and when nearly 
all panned down examine closely for fine colors of gold. 

IRON OR COPPER SULPHURETTES.—The best 
way to test these for gold is to boil the powdered mineral 
in strong caustic potash, then wash or pan it out as before 
mentioned, and examine for fine colors of gold. 

CINNABAR.—Mercury is not always, but most always 
combined with sulphur. It may be detected by either the 
dry or the wet way. In the dry way, place some of the 
powdered ore in a test tube with an iron nail, and heat it 
over the lamp fiame, holding over it a bright strip of cop¬ 
per. Take the copper out and rub it with the finger or bit 
of cloth or paper, and it will give a bright luster. 

BISMUTH.—The ore bismuth is more fusible than lead, 
and is easily reduced in the yellow flame of the blowpipe; 
with carbonate of soda gives a reddish-white metal; when 
dissolved in nitric acid, water will precipitate as white 
oxide. This is the only metal besides lead which can be 
cupelled alone. ' i 

CHROMATE OF IRON.—Place some of the powdered 
ore in a test tube with nitric acid and boil. It will color the 
acid green; then filter, and to the filtrate add ammonia, 
which will precipitate in dirty green flakes, which will re¬ 
dissolve in acid compounds of chromium. With the blow¬ 
pipe, will color the borax bead green. The precipitate 
with ammonia—if fused with a little potash and soda—will 
give a yellow mass of alkali chromate. The ore, if fused 
with potash and soda (carbonates), gives a yellow precipi¬ 
tate with lead salts, red with sulphur compounds, and turns 
green by boiling with hydrochloric acid and alkali. 

ARSENIC.—Powder the ore; throw it on live coals or 
a hot shovel, or within the blowpipe flame; it will give a 
garlic smell. 


2o6 examination OF ORES 

SELENIUM.—Test the same as for arsenic and it will 
give a smell of rotten horseradish. 

GYPSUM, HEAVY SPAR—Is an earthy sulphate; 
scratches with a knife and is not affected by acid. The 
best test of sulphur is on silver, but will not smell of it. 

BORATES OR BORAX, OR BORATE OF LIME.— 
Moisten with glycerine, will give a green flame with the 
blowpipe; or treat with sulphuric acid in a dish, then add 
alcohol and set fire to it and a green flame will appear. 


GloSvSary or the MOvST Important Minerals, giving the P'ormul^, Hardness, Specific Gravity, 

AND Behavior with Acids. 

I=insoluble in or unaffected by acids; S=soluble in or decomposed by acids. 



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Rhomb, 
























































Glossary of the Most Important Minerals—C ontinued. 


4, 

i' 


<v 

■*-> 

u 

Sr 

cc 


Oi 


o 

c« 


r 


a 

<v 



a 

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u 

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b/D'S 

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(V xi 


Tj- (N CS CS 

I I I I I 
00 o^ m — 



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9k C 


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OJ —. 


X 

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d) 


lO 

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O lO 


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rO rO lO fM .• • ^O fN 

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. . ^ ^ ^ . . 
CN (N fN / Tt *• • <N <^l 

ro 


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! i 
O 


7 9 

lo 'i' 


uo 

CN M 


0^ H- (N 

— 'B* ''O (N 

i : ; i ; ■ 

O O vO X' 


lO^O 


ro fO ■- 


\0 


M 


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rf 00 
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03 


a 

o 

Pp 


wo 'Tf 

T to • 1 ^ wovo lo tr- 

I .ipuo! • 1 —vO • I 
1 wo 1 lO^ lO CN 

WO • lO ro 


<> 

lO 


lo^/ 

wo 


wo 

rj- 

lo .lo ^ 


VO 

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lO wo XO • 

w j 




q o 

i I 
wo wo 

rr WO 


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lO ‘O WO'O 

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lO i-i wo 


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a •a>.§ 

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CC 05 <3^ 

XXX 
CL 0 } c /1 


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Gi.ossary ok The Most Important MikeraEvS— Continued. 


c/2 

w 

'o 

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a; 

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Glossary of the Most Important Minerals— Concluded. 


tfi 

■73 
• ^ 
O 
rt 

'■C 

IV 
cn 
O 
P- 

Q 

O 

o 

V 

Vh 

C 


o; 

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cr. 


u 

cC 


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+-> 

c/3 


c« 


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o 


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b 4 t ^ 

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"P ^ 
P O 

25 



VO >- CO M X — X 

CO rl- ro <N X (N (N 
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-tt lO “ X o^x 

ro X rO (N ro “ CN 


<N 1' 

• ♦ • • • 

t o X • (N 

I ! I ; X ! 
XX X 

^ (N CN 


rO ^ <N 


X X X 
X 

! ! : ! 

X rO CO (N i-H 

’ (N (N 


XX irc 
X 


X 
X ^ 
rO X 


•c 

"i" X • ^ 

! • 'O X ! 

r<^ (N . X 

X 


Tj- X X 
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<N X X *P 
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V 


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CD 


D 


_ O ^ u 

Ph P-i -M ’-Tj -Jp P Oj 

(/} tn (/} w tf) to h* 


'C 

V 

Cti 

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c 6 
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HH 


m 1-^ to m to to to tr^ to to to to to 


V 

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03 V-. 

a p 
o o 
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a; 


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r-H U 
2 

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PL 


H 


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03 ^ Cl, 

nOri'P-'S 

2 M.'r: ^ 

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29 


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biO<d 

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< “O (U 03 

X 9 ^ P 

< ^ u 


o 

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2 o : 

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9 O 

O <u 

X' 2 
2 
X 


x'O 

d 

M 













































212 


LITHOGICAL GEOLOGY 


LITHOLOGICAL GEOLOGY. 

CHARACTERISTICS OL ROCKS—STRUCTURE. 

1. MASSIVE—Like sandstone or granite: breaking 
one way as easily as another. 

2. LAMINATED OR SCHISTOSE—Breaking into 
scales and slabs like paving stone. Schistose is usually re¬ 
stricted to the crystalline rocks like guess and mica schist. 

3. SLATY.—Breaking into thin and uneven plates, like 
roofing slate. 

4. SHALY—Breaking unevenly into fragile plates, like 
the slate or shale of the coal period. 

5. CONCRETIONARY—Having the form of, or con¬ 
taining spherioidal concretions. 

6. GLOBULIEEROUS — Haying isolated globular 
concretions, evenl}^ distributed through the texture of a 
rock. 

7. OOLITE—An aggregation of minute concretions in 
a rock, similar to the eggs or roe of a fish. 

FIRMNESS. 

1. FLINTY—Very hard and breaking with a smooth 
surface. 

2. COMPACT—Well consolidated. 

3. UNCOMPACTED—Like loose earth. 

4. POROUS—So loose or open in texture as to absorb 
water and air readily. 

5. FRIABLE—Crumbling in the fingers. 

CONSTITUENTS. 

1. SILICEOUS—Consisting mainly of quartz. 

2. OUARTZOSE—Containing much quartz. 




LITHOGICAL GEOLOGY 213 

3. OUARTZYTIC—Consisting in part of quartzytic 
rocks, as quartzite, gneiss, etc. 

4. GRANITIC—Like granite (quartz, feldspar and 
mica. 

5. MICACEOLIS—Characterized by the greater pro¬ 
portion of mica. 

6. FELDSPATHIC—Characterized by the greater 
proportion of feldspar. 

7. ARCilLLACEOUS—As clay, or of a clayey nature, 
as shale, etc. 

8. ARENACEOUS—Feebly coherent grains of quartz 

s 

in any rock. 

9. CALCAREOUS—As a mica schist containing car¬ 
bonate of lime, or any rock similar to a limestone. 

10. FERRUGINOUS — Of a red, brown, or yellow 
color due to the presence of the peroxide of iron in scales 
or strains through the rock. 

11. PYRITIFEROUS—Containing crystals, grains, or 
masses, of pyrites, disseminated through the rock. 

12. PUMICEOUS—Like pumice, of a vesicular nature. 

13. GARNETIFEROLTS—Containing garnets, as gar- 
netiferous mica-schist. 

14. BASALTIC—Like basalt (an igneous rock), made 
of material derived from basalt. 

15. HORNLENDIC-—Containing hornblend in great¬ 
er proportion. 

16. HOMOGENEOUS—Having the mineral ingred¬ 
ients not separately distinguishable, but forming a homo¬ 
geneous mass, granular or otherwise, like slate, and shale, 
etc. 

17. AMYGDALOIDAL—Having numerous almond- 
shaped cavities filled with crystals and minerals of a nature 
foreign to the rock, as calcite quartz, and the zedites. 


LITHOGICAL GEOLOGY 


.214 

18. SCORIACEOUS — Slag like; very open inflated 
-cells; slag of a furnace, scoria of a volcano. 

19. GRANITOID—Relating to granite. 

20. GRANULAR—Of a fine or coarse crystalline na¬ 
ture. 

21. PHANEROCRYSTALLINE—Distinctly crystal¬ 
line: as in granite and architectural marble. 

22. CRYPTOCRYSTALLINE — Concealed crystal¬ 
line, as in fine statutary marble. 

23. PORPHYIIIC—Having the feldspar hornblend, 
•or Pyroxene, in distinct and sometimes twin shaped crystals, 
disseminated through the rock mass, speckling it all 
through. 

24. DOLOMITIC—Pertaining to the marbles, fine 
limestone. 

25. CALCITIC—Pertaining to or like chalk. 

26. DOLERITIC—Like dolerite a feldspathic augite; 
trap rock. 

27- TRAPPITIC—Like any of the true igneous rocks; 
as trap, basalt and etc. 

28. VOLCANIC—Like any of the true volcanic rocks; 
as lava, obsidian, etc. 

29. GNEISSIC—Pertaining to the mica of the rock in 
laminated planes or layers, as in gneiss. 

30. SYENITIC—Like a hornblendic granite or syenite. 

31. DIORIIIC—Like diorite; a feldspathic hornblend; 
Trap rock. 

32. AUGITIC—Like augite; a black or dark green rock 
composed of short crystals of pyroxene. 

33. FELDSITIC—Pertaining to Felspar; kaolin; por¬ 
celain clay. 

34. IRACHYnC—Like trachyte; a light colored, 
rough felds])atliic rock, having small crystals of feldspar. 

35. COPROLIIIC—Like “fossil excrements,” some- 



LITHOGICAL GEOLOGY 


215 


times found in phosphate of lime as phosphatic nodules. 

36. CHLORITIC—Like the green stones; pertaining 
to the chlorine they contain. 



2i6 


ORES COMMON IN ROCKS 


METALLIC ORES COMMON IN ROCKS. 

1. PYRITE—Often occurs in cubes, a compound of 
sulphur and iron (53-^3:46.^®7), pale brass yellow color, less 
yellow than copper pyrites, strikes fire with steel. 

2. PYRRHOTITE—An iron pyrites; (40^:60^®) is as 
soft as copper pyrites, but of a pale bronze color. 

3. CHALCOPYRITE — Copper pyrites; an easily 
scratched, deep yellow compound of s. fe. and cu. easily 
crushed into a dark green powder. 

4. GALENITE—Galena, most common ore of lead 
(13.4®—86.6^^.) occurs in cubes of a soft, brittle, lead-gray 
color, also in dodecahedrons and other forms. 

5. SPHALERITE—Zinc blend, (33.® 67^^-) a black, 
brown, or resin yellow crystalline mass, yielding a whitish 
powder. 

6. HEMATITE—Bog iron ore, specular iron ore (fe^ o®) 
in steel gray crystals and masses and deep red earthy masses, 
giving a red powder. 

7. MAGNETITE—Magnetic iron ore (fe^o'^) in mas¬ 
sive iron gray crystals yielding a black powder. 

8. LIMONITE—Hydrous iron ore (2 fe2o^-|-3 H^o); 
black and brown yellow earthy masses yielding a brown 
yellow powder. 

9. MENACCANITE—Titanic iron ore similar in com¬ 
position to Hematite but containing Fitaninm black crvs- 
tals yielding a black powder. 

10. GRAPHITE—Plumbago, black lead (the material 
of lead pencils) and amorphous, shining mass of pure mi¬ 
croscopical carbon crystals. 


MATERIALS OF ORGANIC ORIGIN 217 


MATERIALS OF ORGANIC ORIGIN. 

1. Siliceous—The spicula, teeth, shields, and shells of 
the siliceous sponges, mollusks, diatomes, and polycystines 
which have contributed to the silica of the rocks, and may 
have originated the flints. 

2. Calcareous—The shells of the crinoids, corals, coral¬ 
lines, etc., which have contributed to the formation of phos¬ 
phate of lime and fluoride. 

3. PHOSPHATIC—The bones, excrements, animal 
tissues, shells of crustaceans and of animals, edible grains, 
fruits, etc., and the guano of birds and bats. 

4. CARBONACEOUS—The plants, which have af¬ 
forded mineral oil, coal, and resin. 

5. ORGANIC TISSUES—The flesh of animals some¬ 
times fossil found'imbedded in the mud, composing the 
rock forming phosphates and fluorides of lime. 

(Dana’s Manual and my own notes.) 

For those who wish to obtain only a fair knowledge of 
the more common minerals and metal-bearing rock, I have 
here introduced from J. D. Dana his series of colors, lustre, 
scale of hardness, taste and odor, after which we will insert 
the name and number in series, also the names of the dif¬ 
ferent minerals, and proceed to determine a mineral by that 
method. 


DIAPHANEITY, LUSTRE, COLOR 


j2I8 


DIAPHANEITY, LUSTRE, COLOR. 

Diaphaneity. 

“Diaphaneity is the property which many objects possess 
of transmitting light; or, in other words, of permitting more 
or less light to pass through them. This property is often 
called transparency, but transparency is properly one of the 
degrees of diaphaneity. The following terms are used to 
express the different degrees of this property: 

“Transparent—when the outlines of the objects, viewed 
through the mineral, are distinct. Example: glass, crystals 
of quartz. 

“Subtransparent, or semi-transparent—when objects are 
seen but their outlines are indistinct. 

“Translucent—when merely the edges transmit light 
faintly. 

“When no light is transmitted the mineral is described 
as opaque. 




LUSTRE 


219 


“LUSTRE. 

“The lustre of minerals depends on the nature of their 
surfaces, which causes more or less light to be reflected. 
There are different kinds of intensity of lustre, and also- 
different kinds of lustre. 

“a. The kinds of lustre are six, and are named from^ 
some familiar objects or class of objects. 

‘T. Metallic—The usual lustre of metals. Imperfect 
metallic lustre is expressed by the term submetallic. 

“2. Vitreous—The lustre of broken glass. An imper¬ 
fect vitreous lustre is termed subvitreous. Both the vitre¬ 
ous and subvitreous lustres are common. Quartz possesses 
the former in an eminent degree; calcite often the latter. 
This kind of lustre may be exhibited by minerals of any 
color. 

“3. Resinous-Lustre of the yellow resins. Exam¬ 

ple: some opal, zinc blende. 

“4. Pearly—Like pearl. Example: talc, native, mag¬ 
nesia, stilbite, etc. When united with submetallic lustre 
the term metallic-pearly is applied. 

“5. Greasy—Looking as if smeared with oil. Example: 
elaeolite, some quartz. 

“6. Silky—Like silk; it is the result of a fibrous struc¬ 
ture. Example: fibrous calcite, fibrous gypsum, and many 
fibrous minerals, more especially those which in other 
forms have a pearly lustre. 

“7. Adamantine—The lustre of the diamond. Whem 
submtallic, it is termed metallic adamantine. Example: 
some varieties of white lead-ore or cerussite. 





220 


LUSTRE 


“b. The degrees of intensity are denominated as fol¬ 
lows : 

‘T. Splendent—When the surface reliects light with 
great brilliancy and gives well-defined images. Example: 
crystals of henatite, cassiterite, some specimens of quarts 
and pyrite. 

“2. Shining—When an image is produced, but not a 
well-defined imagke. Example: calcite, celestite. 

‘‘3. Glistening—When there is a general reflection from 
the surface, but no image. Example: talc. 

“4. Glimmering—When the reflection is very imper¬ 
fect, and apparently from points scattered over the surface. 
Example: flint, chalcedony. 

“A mineral is said to be dull when there is a total ab¬ 
sence of lustre. Example: chalk. 




COLOR 


221 


COLOR. 

Kinds of Color.—In distinguishing minerals, both 
the external color and the color of a surface that has been 
rubbed or scratched, are observed. The latter is called the 
streak, and the powder abraded, the streak-powder. 

“The colors are either metallic, or unmetallic. 

“The metallic are named after some familiar metal, as 
copper-red, bronze-yellow, brass-yellow, gold-yellow, steel- 
gray, lead-gray, iron-gray. 

“The unmetallic colors used in characterizing minerals 
are various shades of white, gray, black, blue, green, yellow, 
red and brown. 

“There are thus snow-white, reddish-white, greenish- 
white, milk-white, yellowish-white. 

“Bluish-gray, smoke-gray, greenish-gray, pearl-gray, 
ash-gray. 

“Velvet-black, greenish-black, bluish-black, grayish- 
black. 

“Azure-blue, violet-blue, sky-blue, indigo-blue. 

“Emerald-green, olive-green, oil-green, grass-green, 
apple-green, blackish-green, pistachio-green (yellowish). 

“Sulphur-yellow, straw-yellow, wax-yellow, ochre-yel¬ 
low, honey-yellow, orange-yellow. 

“Scarlet-red, blood-red, flesh-red, brick-red, hyacinth- 
red, rose-red, cherry-red. 

“Hair-brown, reddish-brown, chestnut-brown, yellowish- 
brown, pinchbeck-brown, wood-brown. 

“A play of colors: This expression is used when several 
prismatic colors appear in rapid succession on turning the 


222 COLOR 

mineral. The diamond is a striking example; also specious- 
opal. 

“Change of Colors—When the colors change slowly on. 
turning in different positions, as in labradorite. 

“Opalescence—When there is a milky or pearly reflec¬ 
tion from the interior of a specimen, as in some opals, and' 
in cat’s-eye. 

“Iridescence—When prismatic colors are seen within ai 
crystal; it is the effect of fracture, and is common in quartz. 

“Tarnish—When the surface colors differ from the in¬ 
terior; it is the result of exposure. The tarnish is described* 
as irised when it has the hues of the rainbow.” 

TASTE. 

Taste belongs only to the soluble minerals. The kind& 
are: 

‘T. Astringent—The taste of vitriol. 

“2. Sweetish-astringent—The taste of alum. 

"3. Saline—Taste of common salt. 

“4. Alkaline—Taste of soda. 

“5. Cooling—^Taste of saltpetre. 

“6. Bitter—Taste of Epsom salts. 

“7. Sour—Taste of sulphuric acid. 

“Odor is not given off by minerals in the dry, unchanged 
state, except in the case of a few gases and soluble minerals. 
By friction, moistening with the breath, the action of acids, 
and the blowpipe, odors are sometimes obtained which are 
th’ s designated: 

“1. Alliaceous—The odor of garlic. It is the odor of 
binning arsenic, and is obtained by friction, and more dis¬ 
tinctly by means of the blowpipe, from several arsenical 
ores. 

“2. Horse-radish Odor—The odor of decaying horse¬ 
radish. It is the odor of burning selenium, and is strongly 



COLOR . 


223 

perceived when ores of this metal are heated before the 
blowpipe. 

“3. Sulphureous—Odor of burning sulphur. Friction 
will elecit this odor from pyrites, and heat from many sid- 
• phides. 

“4. Fetid—The odor of rotten eggs or sulphuretted 
hydrogen. It is elicited by friction from some varieties of 
quartz and limestone. 

“5* Argillaceous—The odor of moistened clay. It is 
given ofif by serpentine and some allied minerals when 
breathed upon. Others, as pyrargillite, afford it when 
heated.” 

l o discover the hardness of a mineral, it is necessary to 
find out which of the typical specimens of the scale of hard¬ 
ness is scratched by it. 

1. Talc (such as soapstone), easily scratched by the 
finger nail. 

2. Rock salt (also gypsum, zinc, etc.), not easily 
scratched by the nail, nor can they scratch a copper coin. 

3. Calc spar (transparent), both scratches, and can be 
scratched by a copper coin. 

4. Pluor spar, not scratched by a copper coin, and does 
not scratch glass. 

5. Apatite, with difficulty scratches glass, and is easily 
scratched by a knife. 

6. h'eldspar, scratches glass, and is not easily scratched 
by a knife. 

7. Quartz, not scratched by a knife and easily scratches 
glass. 

8. Topaz, harder than flint. 

9. Corundum is emerald. 

10. Diamond, which scratches everything. 


224 


GRAVITY OF MINERALS 


1. 

2 . 

3 - 

4 . 

5 - 

6 . 

7 - 

8. 

9 - 

10 . 

11. 

12 . 
13 - 

14. 

15. 

16. 
17 - 

18. 

19. 

20. 

21. 

22. 

23- 

24. 

25- 


SPECIFIC 

GRAVITY OF MINERALS 

• 

Asphaltum 

. I . 

1.8 

Graphite . . 

. 2. 


Brucite . .. . 

. 2. 

3-5 

Orthoclase 

. 2.5 

2.6 

Oiiartz .... 

. 2. 

6. 

Calcite .... 

. 2. 

72. 

Apatite . . . 

. 2.9 

3-2 

Pvroxine . . 

. 3-2 

3-3 

Titanite . . . 

. 3-15 


Garnet . .. . 

. 3-15 

4-3 

Fluorite . .. 

. 4 - 


Sphalerite . 

. 3*9 

42. 

Perofskite . 

. 4.03 

41. 

Brookite . . 

. 4-03 

41. 

Rutile . 

. 4-2 


Barite . 

. 4-5 • 


Pyrite .... 

. 4-9 


Magnetite . 

. 4-9 

52. 

Antimony . 



Cassiterite . 

. 6.4 

7-1 

Galena . . . . 

. 7-5 


Copper . . . . 

.8.9 

• 

Mercury . . 

.13- 

5 - 

Platinum . . 


19. 

Iridosmine 

. 19-3 

21. 




























SCALE OF COLOR 


225 


SCALE OF COLOR. . 

White. 

1. Snow-white.Aragonite. 

2. 1 in-white.Antimony. 

Gray. 

3. Pearl-gray.Talc. 

4. Ash-gra}.Zoisite. 

5. ’Pure lead-gray.Galena. 

Black. 

6. \ elvet-black.Tourmaline. 

7. Brownish-black.Cannel coal. 

8. Iron-black.Franklinite. 

Blue. 

9. Azure-blue.Azurite. 

10. Violet-blue.. Fluorite. 

11. Indigo-blue.\dvianite. 

Green. 

12. Verdigris-green.Garnierite. 

13. Emerald-green.Emerald. 

14. Olive-green.Olivine. 

Yellow. 

15. Sulphur-yellow.Sulphur. 

16. Honey-yellow.Copalite. 

17. Orange-yellow.Wulfenite. 

18. Dark brass vellow.Chalcopyrite. 

Red. 

19. Blood-red.Zincite. 

20. Carmine-red.Chalcotrichite. 

21. Rose-red.Rose quartz. 

22. Copper-red.Copper. 

Brown. 

23. Reddish-brown.Jasper. 

24. Hair-brown.Titanite. 

25. Yellondsh-brown.Opalized wood. 



























226 


MINERAL ANALYSIS 


The proper way is first to construct the following blank 
and note in each place the physical properties and chemical 
reactions of all the tests made, then consult Dana under 
each heading of color, hardness, lustre, fracture, touch, 
taste, cleavage, odor, specific gravity, etc. By this means 
you will soon learn how to classify all the more common 
ores and minerals. 

MINERAL ANALYSIS. 


Work Patiently; Observe Every Characteristic and Change 

Carefully. 


PHYSICAL PROPERTIES. 


Form.. 

Color. 

Lustre—Kind. . 

Degree 

Hardness. 

Fracture. 

Touch. 

Taste. 

Rare Props. .. . 


Structure... . 
Streak. 

Transparency 

Tenacity. 

Cleavage. . , . 

Odor. 

Sp. Gr.,. 


CHEMICAL REACTIONS. 


Solubility. 



FI., Color.. 



Closed Tube. 



On Ch.,. 



With soda on ch.,. 



Borax bead—O. F. . . . 

. ... Hot . 


R. F.... 

. ... Hot . 


Phos. bead—O. F. .. . 

....Hot . 


R. F.... 

Remarks . 

.... Hot . 





NAME. 

Locality 


Composition 
Date. 












































CHEMICAL REACTIONS 


227 


To Ascertain the Characteristics of Any Species.—Look 
in the list for the species number, and by this the species 
can be found in its order in the “Table of Species.” 

To Determine Any Alineral.—Test the hardness with a 
file, or, better with the minerals in the scale of hardness. 
It will be found in one of the columns of the “Table of 
Hardness.” Then, determining the color, we look in the 
column of this color in the “Table of Color” and find that 
there are only a few of the numbers of the previously ascer¬ 
tained hardness in this column; then, determining the 
crystalline form or specific gravity, we eliminate others, 
bringing it finally down to one or two, which we find in their 
order in the “Table of Species,” and compare their quali¬ 
ties. Take Cuprite as an example. We easily find that its 
hardness is 3.5 to 4. It must be in the column headed 3.5 
to 4, or 4 to 4.5. Its color is cochineal red. Its crystalli¬ 
zation is I, streak 77-71. Cuprite is the only one agreeing 


228 CHEMICAL REACTIONS 

with these readily recognized characteristics. As another 
common mineral, take green tinorspar in cubes. Its hard¬ 
ness is 4, its color 4, its crystallization i. Its cleavage is 
B. octohedral; 159 is the only mineral combining these 
qualities. 

One will be assisted in forming an opinion as to the prob¬ 
able identity of the mineral under consideration by remem¬ 
being that in each column of the numerical tables the most 
common minerals form the first-third of each class. 

Again we will examine a mineral which is quite common 
in Oregon. Uraninite (uranium oxide) is the ore usually 
found by pros])ectors and generally occurs in connection 
with lead and silver ores, very rarely in masses. The crys¬ 
tals are octahedrons. The color may be gray, brown, or 
velvet black, and sometimes has a lemon yellow coating of 
uraconite. It is rarely found as a pure ore. The hardness 
is six and the gravity ten, being softer than quartz, which 
is seven, and heavier than galena, which is 7.25. It will 
scratch about as easily as ordinary feldspar, which is six to 
seven. It is hard, but slightly malleable. With the oxidiz¬ 
ing flame of an ordinary blow]:)i])e an equal amount of the 
ore and borax will give a red scoriae when hot and yellow 
or gray when cold. Reduced to a powder it will dissolve 
very slowly in nitric acid. The streak or powder formed 
by scratching with file or point of knife is black. It has 
but little lustre, being dull or sub-metallic. Uraninite 
(uranium oxide) is the only one which answers this de¬ 
scription. 


HLOWI^IPE ANALYSIS 


229 


BLOWPIPE ANALYSIS. 

The following' method has been devised and arranged by 
J. S. Phillips, M. E., for the beginner, that he may be 
enabled to distinguish the useful minerals without puzzling 
over chapters of complicated reading matter and reactions 
in qualitative analysis, which can be understood only after 
a long course of study and much practice. 

Plowever, he should be acciuainted with the blowpipe, and 
know the difference between the oxidizing and the reducing 
flame; the discrimination on charcoal; the platinum wire 
loop, and the use of glass tubes, open or closed, over a 
spirit lamp. 

Before commencing the tests write these names; 

Antimony, Chromium, Lead, Sulphur, 

Cobalt, 

Copper, 

Iron, 

With the manganese, quartoze, and lime rocks, and then 
proceed as follows: Prepare some finely pulverized borax. 
and some phosphate of soda, and, having first brought the 
platinum wire loop to a red heat, touch it to the pulverized 
borax, and again hold it in the flame until it is melted and 
forms a transparent borax bead; touch it to the ore to be 
tested and a glass will be formed. 

Carbonate or phosphate of soda is to be fused in the same 
manner until the bead is formed on the platinum wire, and 
then testing the ore as above described. 

“Thoroughly fuse some of the finely pulverized ore with 
carbonate of soda, within the small terminal eye or loop of 


Arsenic, • 
Bismuth, 
Chlorine, 


Manganese, Tellurium, 
Mercury Tin, 

Nickel, Zinc. 



230 BLOWPIPE ANALYSIS 

platinum wire, in the oxidizing flame; and notice the color 
of the glass. 

“If the glass is pale yellow? Chromic acid is present, 
from some chromate ore. 

“If the glass is of a bluish green? It has been produced 
by manganese. 

“If of a copper red? From copper reduced by this flux. 

“If of a lead colored enamel? From reduced lead. 

“If not thus colored, erase chromium and manganese 
from your list and test for the remainder. 

“Fuse in similar manner with borax. 

“If the glass is blue? The mineral is cobalt 

“If amethyst? Manganese. (But this would not be 
present if the carbonate of soda failed to show it.) 

“If of a reddish brown? Nickel. 

“If neither color? Expunge cobalt, iron, and nickel 
from the list. 

“Place a small piece of the mineral, of about the size of a 
grain of wheat, upon unfluxed willow or pine charcoal, and 
subject it to the oxidizing flame of the blowpipe, until an 
intense heat is produced, which continue for about one 
minute, (and when cold it may be applied to the magnetic 
needle, as a collateral test for iron.) 

“If there is no white, or yellow oxide, deposited on the 
coal, the specimen does not contain antimony, arsenic, bi¬ 
smuth, lead, tin, tellurium, or zinc, and those may be also 
erased from the list. 

“If you wish to examine for the rocks, do so now. 

“Quartz scratches glass, before and after strong ignition. 

“Lime would now dissolve, or slack, in water. 

“Magnesia and alumina, when moistened with a drop of 
the ‘solution of cobalt’ and again strongly heated, will re¬ 
spectively show their characteristic flesh, or blue colors. 

“If a white oxide deposits on the charcoal, at some dis- 


BLOWPIPE ANALYSIS 231 

tance from the test sample, it will be from antimony, ar¬ 
senic, or tellurium. 

‘‘Antimony has a pleasant, flower-like odor; arsenic, a 
disagreeable garlic stink; and the oxide of tellurium will 
burn off with a green flame, before that from the blowpipe. 

‘‘If the oxide on the charcoal is white, and close to the 
test sample, it is produced from tin. 

“If the oxide is yellow when hot, and white when cold, 
it is that of zinc. 

“The oxide of tin, when moistened with ‘solution of co¬ 
balt,’ and re-heated before the blowpipe, becomes of a 
greenish blue color; whilst the oxide of zinc, when thus 
treated, changes to a bright green. 

“If the oxide on the charcoal is yellow, it is either from 
lead or bismuth. Smelt on charcoal with carbonate of 
soda, and these minerals will thus be reduced to metals. 
Bismuth is very brittle, and lead very ductile under the 
hammer. 

“You have now thoroughly tested for all but chlorine, 
copper, mercury and sulphur. 

“Copper was alluded to as coloring the first bead of car¬ 
bonate of soda, but it may now be further tested and more 
effectually reduced on charcoal, when fluxed with, say, 
equal parts of soda and sugar, to irregular nuggets of red 
metal. 

“It may also be detected in very small quantities when it 
has been first roasted in flame, then moistened with hydro¬ 
chloric acid, and re-flamed; as it first gives the blue flame, 
from the chlorine of the acid, then finishes with the beauti¬ 
ful green flame of the copper. 

“CHLORINE.—Fuse in the platinum wire a bead of mi- 

crocosmic salt, with as much oxide of copper (or any cop¬ 
per ore thus oxidized) as it will absorb, then add the liquid 
or solid, that is to be tested, and place it into or before the 


232 BLOWPIPE ANALYSIS 

flame; if chlorine is present it will soon show its charactei- 
istic bine. 

“SULPHUR.—Lay the first bead formed with carbon¬ 
ate of soda, or any other of the slags from the smeltings 
with that flux, on a moistened silver coin, and if the ore is a 
siilphnret, it will, by forming the soluble sulphate of soda, 
stain the bright silver, from brown to black, according to 
the quantity of sulphur present, or time given for the dis¬ 
coloration. 

“MERCURY.—Place a small piece of the raw ore on a 
gold or copper coin, and impinge the flame from the blow¬ 
pipe thereon, for a few seconds, so that the heated current, 
beyond the test sample, may pass close down upon the cold 
coin, when—if it be an ore of mercury—its flame will con¬ 
dense and amalgamate the surface of the metal, which can 
be more distinctly observed, after the coin has been rubbed 
with a wet finger. The coin may be again cleaned by 
warmth. 

“Thus, the qualitative analysis of the profitable base 
minerals may be readily and thoroughly completed, by men 
knowing nothing of minerals at sight, and the particular 
metal, or metals, found, may be then assayed for correct 
quantity, by either of the convenient modes. 

“The short abstract statement of operations for testing 
by the above mode, as given beneath, may be easily remem¬ 
bered. 

“i. Test, with carbonate of soda in platinum loop, for 
colored beads, of chromium, manganese, copper, and lead. 

“2. Test, in similar manner with borax, for colored 
beads, from iron and nickel; and also look for collateral 
amethyst color, of manganese. 

“3. Test, on charcoal, for iron, by the magnetic needle; 
for the oxides of antimony, arsenic, bismuth, lead, tin, 
tellurium, and zinc, by their colors, etc., etc.; and for the 


BLOWPIPE ANALYSIS 


233 

rocks, of quartz by hardness, lime by its solubility, and of 
magnesia and alumina by the flesh and blue colors pro¬ 
duced by ‘nitrate of cobalt’ solution. 

“4. Test for copper, by actual reduction, and color of 
its flame when dissolved in hydrochloric acid; for chlorine, 
by a copper saturated bead of microcosmic salt, by its blue 
flame; for sulphur, by fusion with carbonate of soda, and 
dissolving the mass on a silver coin, by its brown color; 
and for mercury, by hot blast to the sample when placed 
on a gold or copper coin, by its amalgamation.” 


234 


LEAD BLAST 


CALCULATION OF LEAD BLAST FURNACE 

CHARGES. 

This is a very complicated matter for some of the 
charges which work well in one part of the country will 
not do in another section, owing, probably, to the amount 
of alumina or zince present which is seldom taken into con¬ 
sideration. Not only must the charge be so calculated as 
to have a sufificient amount of lead, but that the bullion will 
be of a proper grade. 

Only a few years ago a 20 per cent lead charge was con¬ 
sidered necessary in order to make a good slag, but now a 
12 per cent charge of lead is considered quite sufficient. It 
must be regulated by the supply of ore on hand, or what 
may be expected to arrive. Oftimes the metallurgist is 
blamed for not making a clean slag when the chemist is 
really at fault for not properly sampling and analyzing the 
ore. 

TABLE FOR VARIOUS TYPES OF SLAG. 


SiO FeO CaO ZnO 
Notation. Per Cent. Per Cent. Per Cent. Per Cent. 

A. 34 29 28 

B. 34 34 24 

C. 34 34 18 6 

D. 30 40 20 

E. 30 48 12 

F.25 to 30 54 6 


A is a good slag which is generally used in Utah. 

B is also considered most effective; a great favorite in 
Utah. 








LEAD BLAST 


235 


C is a Colorado slag, and runs well even with zinc. 

D is called a half slag; has been extensively used in Col¬ 
orado and Utah.: 

E is what is known as a quarter slag. 

F is only recommended where there is plenty of iron and 
dry ore is not available. 

The weight of fuel to be used will depend upon the char¬ 
acter of the charge, the fusibility of the slag, the altitude 
of the place, the character of the coke or charcoal used, and 
the dimensions of the furnace. 

The coke or coal used is from 12 to 25 per cent of the 
total weight of the ore taken; some of the sulphur may act 
as a fuel, which must be taken into consideration. The 
amount of lead will affect the fuel, a high lead charge re¬ 
quiring less; all these things must be considered by the 
metallurgist, and he be given time to practice on his charge, 
but invariably when a metallurgist is employed by inexpe¬ 
rienced men to run a furnace, if by any cause there is a 
failure to come up to the requirement, he is discharged and 
another employed to do the same thing. 


f 


I 



236 


WORKING TEST OF 


WORKING TEST OF GOLD OR SILVER ORES. 

Many times the prospector desires to make a working 
test of his ore, that he may know the probable results by 
mill process. This can readily be done by finely pulveriz¬ 
ing a few pounds of the ore, and, if free from all sulphurets 
testing it at once by amalgamation. 

But if the ore is a sulphuret it must first be roasted with 
charcoal and carbonate of ammonia and the ore completely 
oxidized before any amalgamation can be had. 

If the ore is a sulphuret of silver in any form it may be 
chloridized by roasting it with salt until the ore has a red¬ 
dish appearance of iron rust when cold. The chloridizing 
of a small lot can be done in the muffle, or if of several 
pounds an old box stove can be made to answer as a re- 
verbatory furnace, and the ore constantly stirred during 
chloridization. When sufficiently roasted and it has no 
smell of sulphur it may be withdrawn from the fire and 
cooled, then placed in a leaching cloth in a large funnel and 
over it poured a strong hot solution of common salt, or a 
cold solution of hypo-sulphite of soda, which will leach out 
all the chloride of silver into a receiving vessel when it can 
be at once precipitated with a solution of polysulphide of 
sodium and collected on a filter and smelted into a button 
of lead and cupelled. 

But if the ore is a gold sulphuret ore it can only be roast¬ 
ed with charcoal and carbonate of ammonia, until no 
further smell of sulphur is noticed. 

Then weigh out from one to five pounds as desired, and 
treat about a half pound at a time, which will be sufficient 
for an ordinary Buck’s grinder ; add hot water just so it will 


GOLD OR SILVER ORES 


237 

be the consistency ’of nmd; sift in a little quicksilver 
through a buckskin and add one or two pennyweights of 
sodia amalgam, and grind for 15 or 20 minutes, then wash 
out the mortar into a pan, and continue until all the pulp 
is worked up, when it may be vanned down to an ounce or 
so, the quicksilver collected and strained through buck¬ 
skin, the amalgam retorted on a shovel, and the gold 
weighed and calculated per ton. 

It is frequently the case that there will be more or less 
globules of foul quicksilver left after vanning; in such a 
case it is best to dry the vannings, including the amalgam, 
and assay it in the usual way for free-milling ore and from 
the resulting bead calculate results. 

Many think that by milling and working 500 or i,ocK>< 
pounds of ore by mill will give them accurate milling re¬ 
sults, but this is a mistake, for any one who knows any¬ 
thing about milling gold rock, knows that there is always 
a loss in cleaning up a mill, and this loss is as much from 
cleaning up a 2,000-pound run as it would be on a run of 
ten tons. Suppose we mill one ton of 2,000 pounds of 
20-dollar rock and the loss in cleaning up the mill is $5.00, 
the loss is 25 per cent, leaving only $15.00 per ton as a 
working test. vSuppose we mill ten ton^, the loss is no 
more than $5.00 on the whole lot, which is only 2^ per cent 
against 25 per cent on the one ton. 

It is much better to select 30 or 40 good average sam¬ 
ples from a mine and take them to a good, reliable assayer- 
who is equipped with a first-class balance and take his re¬ 
sults as an average, then throw off 15 per cent for milling,, 
and the result will be far more satisfactory than any mill- 
insr test unless vou mill ten tons or more. 

o 





238 


ASSAYING SOLUTIONS 


ASSAYING SOLUTIONS. 

Many times it is necessary for us to determine the 
amount of gold in a given quantity of solution, either in 
cyanide or chloride solution. To do this, take some sheet 
lead c. p., lay upon it a square block of wood about 2^ 
inches square, and you have a convenient measure to cut 
your lead, the block acting as a guide for your knife to 
form a square piece of lead. Now make another block of 
•about inches square, over this fold the peice of sheet 
lead, pressing the corners together in the form of a triangle. 
If a little care is exercised in bringing the corners together 
evenly, the tray when completed, will be of nearly equal 
height on all sides and hold fluid full to the brim. You 
now have a square tray, A very convenient quantity of 
the solution to evaporate down is two assay tons. Take 
a 50 c.c. graduate and fill with two assay tons of solution, 
pour it carefully into the lead tray, and evaporate it down 
on a stove or over any convenient flame, boiling lively. 
Add silver if you wish to ascertain gold alone, and cupel, 
part the button obtained and weigh. If fifty divisions on the 
beam of your assay balance corresponds with one milligram 
weight in the pan, then each division on the beam will 
mean one one-hundredth of a milligram for your gold but¬ 
ton. The advantage of using two assay tons of the solu¬ 
tion then, is that in weighing no calculation is necessary. 
You have simply to register the actual reading of the 
beam. 



ORE IN SIGHT 


2o9 


ORE IN SIGHT. 

^‘ORE IN SIGHT,” may be defined as that contained in 
blocked portions of the deposit, each of which is so clearly 
exposed by sections on several sides between the levels run, 
that the limits, continuity and value of its contents may be 
determined and relied upon with reasonable certainty. Such 
are so exposed, may be considered a proved resource, ready 
for extraction and susceptible of expression in terms of net 
profit. 



240 


EXTRACTING COPPER 


EXTRACTING COPPER BY CHLORIDIZING. 

Sulpliurets of copper ores can be profitably worked by 
breaking the ore np into small pieces the size of a hen’s 
egg, and piling alternately in layers of wood and burning 
for several days. This volatilizes sufficient sulphur to ren¬ 
der the rock more friable for crushing and pulverizing in 
any iron mill. 

The finely pulverized ore is now subjected to a chloridiz- 
ing, roasting with sufficient salt to change all the copper 
to a chloride, which requires some fifteen minutes after the 
proper temperature has been reached under continued stir¬ 
ring. 

The roasted charge is now placed in vats and the chlo¬ 
ride of copper is dissolved out with hot water, filtered into, 
or allowed to settle and run into another tank or vessel, 
and precipitated with metallic iron or with caustic lime 
water; it is then dried and pressed into cakes and is readw 
for the smelter. 



ESTIMATING PERCENTAGE 


241 


ESTIMATING PERCENTAGE OF SULPHL'RETS 

IN OUARTZ. 

To estimate the amount of sulpluircts in quartz, take 
10,000 grains or 20,8 ounces troy of crushed rock, so that 
it will pass through a 40-mesh screen. Pan it down very 
carefully in a gold pan or other dish. Dry and weigh. 
Each grain of sulphurets will ecpial one-hundredth of i per 
cent. 

Suppose the sulphurets weiglied only 40 grains, then the 
ore contained only 2-5 of one per cent per ton; if the ore 
contained 5 grains of suli)hurets there would be one per 
cent of the sulphurets. Su])pose 500 grains of sulphurets, 
then we would have 5 per cent of sulphurets per ton, or if 
750 grains of sulphurets, then 7J per cent per ton, etc. 

If the sulphurets were worth $100 per ton the value of 
sul])hurets in each ton would he—for the 2-5, $ .40 per ton. 
If we obtained 5 grains it would he $1.00 per ton. If \ve 
ol tained 500 grains the value would be $5.00 per ton, etc. 
( f course if the ore is richer the values will be increased in 
that proportion. 


242 


USEFUL DATA 


USEFUL DATA. 

TO MAKE SILVER AMALGAM. 

Silver amalgam is better to use on copper plates than; 
quicksilver alone, and a little soda amalgam may be used 
in the battery with it, occasionally. 

To make silver amalgam take three parts of pure silver 
rolled thin and drop it into one part of quicksilver; one- 
fourth of an ounce of this amalgam will cover each square 
foot of surface to be amalgamated, and should be well 
rubbed in. 

If pure silver cannot be had it can be made from silver 
coin by dissolving in dilute nitric acid in a porcelain dish 
and evaporating to dryness over a water bath. Heat, the 
dry mass gently until it fuses and all the bluish tint has 
changed to grayish black, which shows that the copper 
alloy in the coin has become an insoluble oxide. Then 
dissolve the mass in as little water as possible and filter into 
a glass jar, adding the quicksilver required, then dropping 
in some bright strips of sheet iron; the silver will deposit 
as metallic silver and form an amalgam with the quicksil¬ 
ver. Let it stand two or three days and the silver will all 
be deposited and the amalgam formed ready for use. 

To reduce grammes to grains, multiply by 15.432. 

To reduce grains to grammes, multiply by .0648. 

To reduce ounces to grammes, multiply by 28.349. 

To convert degrees of centigrade thermometer to Fahr¬ 
enheit, multiply by 9, divide by 5, then add 32. 

To convert degrees of Farenheit thermometer to centi¬ 
grade, first subtract 32, then multiply by 5, and divide by 9. 

To determine the specific gravity of minerals or other 


I 

I 


USEFUL DATA 243 

substances, weigh in air, then in water, and divide the 
weight in air by the difference. 

“The average fineness of gold in Oregon is 875.5. 

I grain of pure gold is worth. $ 0.0430663 

I gramme of pure gold is worth. 0.6646X 

I ounce Troy of pure gold is worth. 20.671791 

I pound, average, of pure gold is worth. . . 301.46X 

I ton (2000 lbs. = 29166.6 oz. Troy).602927.36 

cubic inch (10.12883 oz. Troy). 209.38 

cubic foot (17502.62 oz. Troy).361808.64 

The heaviest substance known is the metal osmium, 
whose specific gravity is 22.477, while that of gold is 
$19,265, lead 11.367, iron 7.79, and lithium—the lightest 
solid—is only 0.594. Osmium is also the most infusible of 
the metals. It resists the oxyhydrogen flame of 3550° 
Fahr., in which ])latinum and iridium flow, and is even al¬ 
most entirely unaffected by the electric arc, which readily 
melts the extremely refractory ruthenium. It was discov¬ 
ered by Tennant in 1803, and is found in iridosmine and 
platinum. 

Definition of an Acid.—An acid molecule is one which 
consists of one or more negative atoms united by oxygen 
to hydrogen. Recognized by turning certain vegetable 
blues to red. 

Definition of a Base.—A basic molecule consists of one 
or more positive atoms united by oxygen to hydrogen. 
Bases restore the color to any vegetable blue which has 
been reddened by an acid. 

The value of gold per oz. is calculated from the basis that 
387 oz. of pure gold (1000 fine) is worth $8000. Hence i 
oz. is worth $20.671834625, and the i-iooo of an oz. (deci¬ 
mally expressed as .001) is worth $0.020671834625. 

What we usually call fineness, therefore, is simply the 
weight of fine metal contained in a given quantity of mixed 










244 


USEFUL DATA 


metals or alloys. For instance, in a gold or silver bar 
which is reported to be 850 fine, it is simply meant that in 
1000 parts by weight, 850 are fine gold or fine silver, as the 
case may be. 

In onr mints, the value of gold is computed from stan¬ 
dard weight ; that is, gold which is 900 fine, that being the 
fineness of onr gold coin as required by law. The formula 
in this case is, 43 oz. of standard gold are worth $800. 
Hence, multiply standard oz. by 800, and divide by 43, and 
you obtain the value. 

Example—Take 126 15-100 oz. at 856 fine, and we ob¬ 
tain the result thus: 

126. 15 oz. 

856 fineness of gold. 


756 90 
6 307 S 
100 920 


U. S. standard,900) 107,984.40 oz. of fine gold. 


119,982 oz. standard gold. 
800 


43)95.9^5-600 


$2,232.22 value. 

To find value per oz., divide total value ($2,232.22) by 
standard oz. (119,982) and you have $18.60^^, which is the 
value of I oz. of gold at 900 fine. 










ASSAY TABLE. 


For Twenty Grammes of Ore. 


Bead Points. 

Ounce in a Ton 
of the Ore. 

Value in Gold 
(Dollars). 

.1 . 

.14583 

$ 3.01464 

.2 . 

.29166 

6.02928 

.3 . 

.43750 

9.04392 

.4. 

.58333 

12.05856 

.5. 

.72916 

15.07320 

.6. 

.87500 

18.08785 

.7. 

1.02083 

21.10249 

.8 . 

1.16666 

24.11713 

.9 . 

1.31250 

27.13177 

1 . 

1.45833 

30.14642 

2 . 

2.91667 

60.29284 

3 . 

4.37500 

90.43926 

4 . 

5.83333 

120.58567 

5 . 

7.29167 

150.73209 

6 . 

8.75000 

180.87851 

7 . 

10.20833 

211.02493 

8 . 

11.66667 

241.17135 

9 . 1 

1 

13.12500 

271.31777 



























ASSAY TABLE. 


For One Assay Ton of Ore. 


Ounces. 

Gold Value. 

Silver Value. 

.1. 

$ 2.0678 

$ .12929 

.2. 

4.1343 

.25858 

.3. 

6.2015 

.38787 

.4. 

8.2687 

.51717 

.5. 

10.3369 

.64646 

.6. 

12.4301 

.77575 

.7. 

14.4702 

.90505 

.8. 

16.5375 

1.03434 

.9. 

18.6046 

1.16363 

1. 

20.6783 

1.29292 

2. 

41.3436 

2.58585 

3. 

62.0155 

3.87878 

4. 

82.6873 

5.17171 


103.3591 

6.46464 

6. 

124.0310 

7.75757 

7. 

144.7028 

9.05050 

8. 

144.7028 

10.34343 

f. 

186.0465 

11.63636 


































]\IETRIC OR FRENCH WEIGHTS 


247 


METRIC, OR FRENCH WEIGHTS. 


Grammes TroyGrs TroyOz 


10 Milligramme 

.0001 

— 


I Milligramme 

= .001 

= .01543 


I Centigramme 

= .01 

= .15432 


I Decigramme 

= . 1 

== 1.5432 


I Gramme 

= I . 

= 15-432 

.032 

I Decagramme 

II 

0 

— 

.321 

I Hectogramme 

= 100. 


3-215 

I Kilogramme 

= 1000. 

— 

32-150 

I Myriagramme 

= I0000. 

— 


I Quintal 

== I00000. 

— 

• 

I Tonneau 

= 1000000. 

— 



PABLE FOR ORE ASSAYS. 


For One 1,000,ow of Ten Grains Obtained. From One 
Ounce Troy, (iives Per 2000 Pounds Average o, 60, 
75 Ounces. 


GOLD. 



Weight. 


ai 

o 

C 

C 


d 

c; 


Q 


d 


- 1 

.00001. 

00 

006 

$ .12 

.00002. 

00 

012 

.24 

.00004. 

00 

024 

.49 

.00005. 

00 

030 

.62 

.00006. 

00 

036 

.74 

.00007. 

00 

042 

.86 

.00008. 

00 

048 

.99 

.00009. 

00 

054 

1.11 

.0001. 

00 

06 

1.24 

.0002. 

00 

12 

2.48 

.000.3. 

00 

18 

3.72 

.0004. 

00 

24 

4.96 

.0005. 

00 

30 

6.20 

.0006. 

00 

36 

7.44 

.0007. 

00 

42 

8.68 

.0008. 

00 

1 48 

9.92 

.0009. 

00 

54 

11.16 

. 001. 

00 

i 60 

12.40 

.002. 

1 

21 

25.01 

.003. 

1 

82 

37.62 

.004. 

2 

i 43 

I 

50.23 

.005. 

3 

03 

62. P 3 

.006. 

3 

1 64 

75.24 

.007. 

4 

25 

IS 7.8 I 

.008. 

4 

86 

10.45 

.009. 

5 

^6 

112.85 


I 


o m 

<=> 

o ^ 


Weight. 


a: 

o 


a; 


o 

a; 


— 

.010. 

6 

07 

$ 125.46 

.011. 

6 

68 

138.07 

.012. 

7 

-29 

150.68 

.013. 

7 

89 

163.08 

.014. 

8 

50 

175.69 

.015. 

9 

11 

188..30 

.016. 

9 

72 

200.91 

.017. 

10 

32 

213.31 

.018. 

10 

93 

225.92 

.019. 

11 

54 

238.53 

.020. 

12 

15 

261.54 

.021. 

12 

75 

263.54 

.022. 

13 

36 

276.15 

.023. 

13 

79 

288.76 

.02.5. 

15 

18 

313.77 

.026. 

15 

79 

326.28 

.027. 

16 

40 

338.98 

.028. 

17 

01 

351.59 

.029. 

17 

61 

363.99 


18 

1 22 

I 376.60 


IS 

1 83 

1 

i 389.21 

1 


19 

1 44 

1 

1 401.82 


20 

1 04 

1 

1 

1 414.22 

.031. 

20 

1 65 

1 

1 426.83 

1 

.035. 

21 

1 26 

1 

! 439.44 

.03'^. 

21 

1 87 

1 452.03 



















































































.037 . 

22 

47 3 

464.45 

.074 . 

44 1 

95 1 

.038 . 

23 

08 

477.06 

.075 . 

1 

45 

1 

56 j 

.039 . 

23 

68 

489.46 

.076 . 

46 

17 

.040 . 

24 

30 

502.28 

.077 . 

46 

77 

.041 . 

24 

90 

514.68 . 

.078 . 

46 

77 

.042 . 

25 

51 

527.29 

.079 . 

47 

99 

.043 . 

26 

12 

539.90 1 

.080 . 

48 

60 

.044 . 

26 

73 

552.30 j 

.081 . 

49 

20 

.045 . 

27 

33 

564.91 1 

.082 . 

49 

81 

.046 . 

27 

94 

577.51 ' 

.083 . 

50 

42 

,047 . 

28 

55 

590.12 ! 

.084 . 

51 

03 

,048 . 

29 

16 

602.73 j 

.085 . 

51 

63 

.049 . 

29 

76 

615.13 

.086 . 

52 

24 

. n?>o . 

30 

37 

627.74 

.087 . 

52 

85 

.051 . 

30 

98 

640.35 

.088 . 

53 

46 

052 . 

31 

99 


.089 . 

54 

06 

. . 

32 

19 


.090 . 

54 

06 

054 . 

32 

80 


.091 . 

55 

28 

055 . 

33 

41 


.092 . 

55 

89 

056 . 

34 

02 


.093 . 

56 

49 

057 . 

34 

62 


.094 . 

57 

10 

057 . . 

35 

23 


.095 . 

57 

71 

059 .. . 

35 

84 


.096 . 

58 

32 

000 

36 

45 


.097 . 

58 

92 

OR1 

37 

0 *^ 


.098 . 

59 

53 

0091 

37 

66 


.099 . 

60 

14 

004 

38 

88 


.100 . 

60 

75 

005 

39 

48 


.200 . 

121 

50 

000 

40 

09 


.400 . 

243 

00 

007 

40 

70 


.500 . 

303 

75 

OOS 

41 

31 


.600 . 

364 

50 

.069 . 

41 

91 


.700 . 

' 425 

1 

25 

070 

42 

52 


.800 . 

486 

00 

071 

43 

13 


.900 . 

546 

75 

079 

43 

74 


1.000 . 

607 

50 

.073 . 

44 

34 






$ 1255.70 























































































































TABLE FOR WEIR MEASUREMENT. 


By permission of the Pelton Water Wheel Co., 121 Main 
^street, San Francisco, I herewith reproduce from the sixth 

edition of their catalogue a cut and description of Miner^s 
inch measurement for measuring the water of a stream by 
a Weir dam, and the table by which the flow can be inter¬ 
preted into cubic feet per minute. Those desiring to use 
water as a means of power would do well to consult their 
catalogue. 


Giving Cubic Feet of Water per minute, that will flow over 
a Weir one inch wide and from | to 20^ inches deep. 


INCHES . 

% 


% 

¥2 

% 

% 

% 

0 . 

.00 

.01 

.05 

.09 

.14 

.19 

.26 

.32 

1 . 

.40 

.47 

.55 

.64 

.73 

.82 

.92 

1.02 

1 

2 . 1 

1.13 

1.23 

1.35 

1.46 

1.58 

1.70 

1.82 

■ 1.95 

3 . 

2.07 

2.21 

2..34 

2.48 

2.61 

2.76 

2.90 

3.05 

4 . 

3.20 

3.35 

3.50 

3.66 

3.81 

3.97 

4.14 

4.30 

5 . 

4.47 

4.64 

4.81 

4.98 

5.15 

5.33 

5.51 

5.69 

6 . 

5.87 

6.06 

6.25 

6.44 

6.62 

6.82 

7.01 

7.21 

7 . 

7.40 

7.60 

• 7.80 

8.01 

8.21 

8.42 

8.63 

8.83 

8 . 

. 

9.05 

9.26 

9.47 

9.69 

9.91 

10.13 

10.35 

10.57 

9 . 

10.80 

11.02 

11.25 

_ 

11.48 

11.71 

11.94 

g 2.17 

12.41 

10 . 

12.64 

12.88 

13.12 

13.36 

_ 

13.60 

13.85 

14.09 

14.34 

11 . 

14.59 

14.84 

15.09 

15.34 

_ 

15.59 

15.85 

16.11 

16.36 

12 . 

16.62 

16.88 

17.15 

17.41 

17.67 

17.94 

18.21 

18.47 

13 . 

18.74 

19.01 

19.29 

19.56 

19.84 

20.11 

20.39 

20.67 

14 . 

- 

20.95 

. 

21.23 

21.51 

21.80 

22.08 

22.37 

22.65 

22.94 

15 . 

23.23 

23.52 

23.82 

24.11 

24.40 

24.70 

25.00 

25.30 

16 . 

25.60 

25.90 

26.20 

26.50 

26.80 

27.11 

27.42 

27.72 

17 . 

28.03 

28.34 

28.65 

28.97 

29.28 

29.59 

29.91 

30.22 

18 . 

30.54 

30.86 

31.18 

31.50 

31.82 

32.15 

32.47 

32.80 

19 . 

33.12 

33.45 

33.78 

34.11 

34.44 

34.77 

35.10 

35.44 

20 . 

35.77 

36.11 

36.45 

36.78 

37.12 

37.46 

37.80 

38.15 


. SupDOse the Weir to be 66 inches long, and the depth of 
water on it to be iif inches. Follow down the left hand 




















































































































































































































































































































EXAMPLE 251 

column of the figures in the table until you come to 11 
inches, then run across the table on a line with the ii, 
until under f on top line and you will find 15.85. This mul¬ 
tiplied by 66, the length of Weir, gives 1046.10, the num¬ 
ber of cubic feet of water passing per minute. 



The term “miner’s inch” is ot California origin, and not 
known or used in any other locality, it being a method of 
measurement adopted by the various ditch companies in 
disposing of water to their customers. The term is more or 
less indefinite, for the reason that the water companies do 
not all use the same head above the center of the aperture, 
and the inch varies from 1.36 to 1.73 cubic feet per minute 
each, but the most common measurement is through an 
aperture 2 inches high and whatever length is required, and 
through a plank ij inches thick, as shown in print. The 
lower edge of the aperture should be 2 inches above the 
bottom of the measuring box, and the plank 5 inches high 
above the aperture, thus making a 6-inch head above the 
center of the stream. Each square inch of this opening 
represents a miner’s inch, which is equal to a flow of ij. 
cubic feet per minute. 








































252 


ASSAY TON WEIGHTS 


ASSAY TON WEIGHTS. 

The Assa}^ Ton Weights is a system made up from a 
com])arison of the Avoirdupois, Troy and Gramme 
Weights, and will be found extremely simple and useful, 
saving a vast amount of calculation and labor. 

The unit of the system is the assay ton=r 29,166 
grammes. Its derivation will be seen at a glance. 

I lb. Avoirdupois=7,ooo Troy grains. 

2,000 lbs.= i ton. 

2,000X7,000=14,000,000 Troy grains, in one ton Avoir¬ 
dupois. 

480 Troy grains=i oz. Troy. 

14,000,000^480=29,166 Troy ozs. in 2,000 lbs. Avoir- 

I 

dupois. 

There are 29,166 milligrammes in one assay ton (A. T.); 
hence 2,000 fcs. is to A. T. as i oz. Troy is to i milli¬ 
gramme. 

Therefore, if i A. T. of ore assays i milligramme of gold 
or silver, the ton contains i ounce Troy. 


GRAIN WEIGHTS 


253 


' CONSTRUCTING THE A. T. WITH GRAIN 

WEIGHTS. 

In constructing' the A. T. on the grain system, it is only 
necessary to remember that in one ton of 2000 pounds there 
are 29,166 Troy ounces. Consecjuently, if we take 291.66 
grains of the ore pulp for the assay, each bead point in 
weight ol)tained in a one-hundredth ])art of a grain repre¬ 
sents one ounce of metal in a real ton of the ore. This is 
very convenient where the ore contains much metal. But, 
for very low grade ores, it is better to double the amount 
(291.66) and take 583.32 grains of the prepared pulp for 
an assay. In that case, each bead point in weight will rep¬ 
resent one-half ounce of metal to the real ton of the ore, in 
either gold or silver. These weights can be prepared and 
accurately determined out of a peice of lead, and the A. T. 
doubled, halved, or quartered, as desired. 

By permission of the Pelton Water Wheel Co., 121 Main 
street, San Erancisco, I herewith reproduce from the sixth 
edition of their catalogue a cut and description of Miner’s 
inch measurement for measuring the water of a stream by 
a Weir dam, and the table by which the flow can be inter¬ 
preted into cubic feet per minute. Those desiring to use 
water as a means of power would do well to consult their 
catalogue. 


I 


I 


I 


EXAMPLE 


254 

In the foregoing work I have followed C. H. Aaron more 
largely than other authors for the reason that I consider his 
methods far the best of all, for practical work. 

Books consulted in the preparation of this work: 

Joseph Le Conte’s Geology. 

F. E. Thorpe’s Chemistry. 

Bowman’s Chemistr3^ 

Thomas Bailey’s Chemistry. 

James D. Dana’s Mineralogy. 

Mining and Scientific Press. 

Mitchell’s Manual on Assaying. 

H. Van F. Furman on Assaying. 

Francis Sutton on Volumetric Analysis. 

J. S. Phillips’ Metallurgists’ Companion. 

Joshua Trimmer’s Analysis of Minerals 
J. M. Craft’s Qualitative Analysis. 


SCHOOL OF MINES 255 

The important and highly remunerative industry of min¬ 
ing has, during the last few years, been prosecuted in the 
Northwest with greatly renewed energy and vigor. 

The renewed activity in the search for and development 
of these great sources of wealth is due to many causes. 
The constantly appreciating value of gold is one cause of 
this activity, it being apparent, under the present economic 
conditions, that though other products may fall in price 
from over-production, the production of gold cannot be 
OT'erdone. The low price of labor, the extension of steam 
trr.nsportation and the highly improved methods for the re¬ 
duction and treatment of ores, are other important factors 
in the new development of the mining industry. 

It is evident that the renewed energy has but now begpm 
and that it will continue to grow until the mining industry 
will be one of paramount importance in the Northwest, en¬ 
gaging the industry of great numbers of our people, and 
calling for the professional employment of a great amount 
of skilled superintendence and knowledge. 

In view of the above well-known facts, the Portland 
School of Mines, Engineering and Assaying has been es¬ 
tablished, in order to give an opportunity to the young men 
and women of the Northwest to prepare themselves for re¬ 
munerative employment in all the different mining activi¬ 
ties that promise a profitable field of professional labor. 


256 


TESTIMONIAL LETTERS 


TESTIMC )\TA.L LETTERS. 

We herewith siil)mit a few testimonial letters from our 
students, some of whom are holding positions of trust and 
responsibility. These letters speak for themselves; 

Walla Walla, Wash., Way 17, 1897. 

J. H. Fisk, Esq., Portland, Oregon: 

Dear Sir—Having taken lessons in assaying under your 
instructions, T beg leave to say that I can cheerfully recom¬ 
mend you as a teacher in all that class of business, for the 
reason that you are better acquainted with the rocks, ores 
and mineral formations of this immediate country than any 
other professor could be at the present time. 

Very respectfully, 

J. P. ISAACS, 
Assayer and (J)re Sampler. 

Bernard Bay, Alaska, July 12. 1897. 

J. H. Fisk, Portland School of Mines: 

Dear Sir—Having pursued a course of study in mining, 
assaying and testing of ores under your instructions, I beg 
to say that I have found the methods used by you of great 
value to me in my practical experience as an assaver, and 
can heartily recommend the same to all others desiring in¬ 
formation in the same line of business. 

Respectfully, 

A. H. PETTIT, 

Assayer for the P.-A. C. & S. M. Co. 



PROFESSIONAL CARD 


257 


• C. M. COOK, 

Assayer, Stevenson, Wash. 

Stevenson, Wash., May 24, 1897. 

J. H. Fisk, Esq., Portland School of Mines, I^ortland, Or.: 

Dear Sir—Having attended your lectures and taken a 
course of study under your instruction the past winter, it 
affords me pleasure to state that, in practical application, I 
have found your formulas for testing, treating and assaying- 
ores of great value, and their efficiency unexcelled by any 
authors on assaying. 

I would cordially recommend the course of study and 
lectures under your instruction and illustration to all desir¬ 
ing practical information in that direction. , 

Respectfully, 

C. M. COOK, 

Assayer. 


Portland, Or., May 13, 1897. 
Mr. J. H. Fisk, Portland School of Mines: 

Dear Sir—We, the undersigned, late students of yours 
in assaying and testing ores, beg to contribute our testi¬ 
mony to your ability and faithful services as a teacher, and 
unhesitatingly and unqualifiedly recommend your methods 
to all others. 

A. E. BORTHWICK. 

MISS I. SEDGWICK. 

ALBERT J. FROELICH. 

H. A. BROWER. 

J. GUSTAFSON. 

OSCAR STARR. 

MISS M. STARR. 

MRS. L. M. COBURN. 

J. W. KILLINGER. 

F. G. BARTON. 

EDWIN WHEELER. 

EDWIN GUERIN. 

GEORGE CURTIS. 

II. B. GRAVES. . 



2 s8 charges for assaying ores 

■ PROFESSIONAL CARD. 

Mines examined, and reports on mines and mining pros¬ 
pects in the Northwest. Charges, $io per day and ex- 
penses. 

Analytical work of every kind, and assaying done by the 
Principal in charge separate and apart from the school, and 
not intrusted to any student. 

CHARGES FOR ASSAYING ORES. 

Assays for Gold and Silver.,.$ i-S® 

Assays for Gold, Silver and Lead. 2.00 

Assays for Copper. i.oo 

Assays for Iron . 3-00 

Assays for Lime . 3-00 

Assays for Sulphur. 3-00 

Assays for Zinc . 3-00 

Assays for Tin. 3-00 

Assays for Antimony . 2.00 

Assays for Arsenic . 5-00 

Assays for Cinnabar. 4.00 

Assays for Bismuth, Cadmium, each. 4.00 

Platinum Analysis . 15-oo 

Test and examination of an ore from.$i to 5.00 

Working test of Free-milling Ore. 5-00 

Working test by Cyanide Process. 5-00 

Working test of Sulphurets by Chlorination. 10.00 

Gold dust melted, cast into bars, assayed and stamped, 
and cashed if desired. 

h"or a large number of Assays a s|)ccial rate will be made. 




















CHARGES FOR ANALYSIS OF COAL 


259 


CHARGES FOR ANALYSIS i)F COAL. 
Test for Water, Coke, \ olatile and Combustible 


Matter I'ix Carbon in Coal.$10.00 

Analysis of the Ashes.. 5-00 

Phosphates and Sulphur. 10.00 

Heating' Power of Coal. i5-00 

Commercial ^Analysis of Coal. .'25.00 

Commercial Analysis of Clays. 25.00 

Commerical Analysis of Mineral Waters. 25.00 

Qualitative Analysis of Mineral Waters. 15-oo 


Analysis of Poisons, post mortem, or otherwise, by con¬ 
tract. 

On sending samples by mail, mark your name on the 
outside, and mai k each sample distinctly, and in a separate 
letter give full instructions. Write your name and address 
])lainly, and send money for each assay by postoffice order 
or with the package of ore. If money is not sent for assay¬ 
ing, returns will be made by express, C. O. D. 

2 J 4 i WASHINGTON STREET, PORTLAND, OR. 











INDEX 


261 


A 

Abbreviations. 

Acid, Definition of. 243 

Acetic Acid . 31 

Alloys . 0 

Alluminum . 192 

Alumina, Test. 200 

Ammonia—Solvent. 31 

Precipitant . 33 

Ammonium—Carbonate-Precipitant . 33 

chloride. 34 

Nitrate, Oxidizing reagent . 37 

oxalate. Precipitant . 32 

sulphide. Precipitant . 33 

Antimony, Blowpipe analysis. 229 

Test . 156 

Argol, Flux . 28 

Arsenic, Assay of. 153 

Test . 205 

Assaying bullion. 45 

Assay, Definition of. 11 

Doree bars, base bars, etc. 50 

of gold and silver ores. 45 

of litharge. 81 

of nickle and cobalt . 141 

proper of a gold bar. 47 

of tin ore. 109 

table of grammes. 245 

table for gold in grains. 248 

for one assay ton of ore. 246 

ton weights. Explanation of. 252 

Assaying Solutions . 238 

B 

Balances . 22 

Barium . 192 

chloride Precipitant . 32 

Base, Definition of. 243 






































2C2 


INDEX 


t. 


Bismuth, Test . 

Black flux . 

Blowpipe analysis . 

Borates or borax .•'. 

Borax flux . 

Bromine, Oxidizing reagent . 

C 

Calciiith .»i. v». *»^ 111 i... ii i . 

Calculating the assay. 

Carbonate—of soda flux. 

ore, Preliminary examination. 

Characteristics of species. To ascertain 

Characteristics of rock structure. 

Charcoal . 

Chlorine, Blowpipe analysis. 

Oxidizing reagent .. 

Chromate of iron, Test. 

Chromium . 

Cinnabar, Test. 

Cerium. 

Citric acid. Solvent. 

Caesium .. 

Constituents of rocks. 

Constructing A. T. with grain weights.. 

Coal analysis . 

Color of minerals. 

Columbium . 

Combination of elements. 

Compounds . 

Converting ore into matte for assay.... 

Copper, Assay of. 

Blowpipe analysis . 

extracting by chloridizing. 

ore. Test . 

Crucible assays . 

assays of gold and silver. 

Cupelling. 

Cyanide process . 

D 

Determination of iron in ore. 

Diaphaneity of minerals. 


Page. 
. 158 
.. 27 
. 229 

206 
26 
.. 37 


. m 

. lo3 
. 26 
. 201 
. 212 
. 212 
. 28 
. 231 
. 37 

. 205 
. 193 
. 205 
. 193 
. 31 

. 194 
. 212 
. 253 
. 169 
. 221 
. 193 
. 8 
. 8 
. 113 
. 114 
. 229 
. 240 
. 203 
. 82 
. 86 
. 96 

. 115 

. 123 
. 218 










































INDEX 


203 


Didymiiim . 

Dressing the crucible . 

E 

Elements . 

Erbium . 

Estimating percentage of sulphurets 
Estimating Sulphurets in Quartz .. 


Firmness of rocks . 

Fluxes used in fire assays. 

Flux for concentrated pyrites. 

for lead ores. 

for ore containing quartz, clay, lime, etc. 

for ore containing 10 per cent, of sulphurets 
for ore containing 10 per cent, of copper... 
Furnace, construction of . 

G 

General formula for ordinary ores. 

Glass, Flux . 

Glossary of the most important minerals. 

Gold and silver ores—Working test of.. 

Test by fire assay. 

Test by wet method. 

Gypsum, Heavy spar, Test of. 

Gold . 

Glucinum. 

Gallium . 

H 


Hardness of minerals .. 

Humid assay of silver bullion.... 

Hydric sulphide, Precipitant. 

Hydrochloric acid, Solvent. 

Hydrogen, Reducing reagent. 

Hydrofluoric acid, Solvent. 

Hydrosodic phosphate, Precipitant 

I 


Page. 

,. 193 
.. 87 


10 

196 

241 

241 


. 212 
26-27 
. 89 
. 120 
. 88 
. 89 
. 113 
. 21 


120 

27 

207 

236 

204 

204 

206 

191 

193 

194 


223 

54 

34 

30 

36 

30 

32 


Implements . 

Iron or copper sulphurets, Test 


14 

205 



































264 


INDEX 


Page. 

Iron, nails, Desulpburizer. 28 

Iron ore. Preliminary examination of. 202 

Indium . 194 

Iridium . 194 

L 

Lead assays . 118 

to make free from silver. 176 

blast furnace charges. Calculation of. 234 

flux. 234 

or galena. Test for . 204 

Granulated . 28 

Sheet . 29 

Tatharge, constituents of. 26 

Flux .». 26 

Assay of . 81 

Lustre of minerals. 219 

Lithium. 194 

M 

Magnesia mixture. Precipitant. 33 

Manganese, Test . 131 

Materials of organic origin. 217 

Melting of gold and silver bullion.39 

in crucible. 91 

Mercury, Assay of . 150 

Blowpipe analysis . 232 

Metal, heaviest known . 243 

Metallic copper. Precipitant. 34 

alluminum Precipitant . 35 

zinc. Precipitant. 34 

Metallic Ores common in rocks. 216 

Metric system, French weights. 247 

Mineral analysis. Blank for. 226 

Minerals, Behavior with acids.202-203 

Mineral, to determine any. 227 

Miner’s inch measurement, Explanation of. 251 

Mixing the charge. 80 

Molybdate solution . 33 

N 

Nickle ore. Preliminary examination. 203 

Nitre or saltpeter flux. 27 









































INDEX 


265 


Page. 

Nitric Acid, Solvent. 31 

Oxidizing reagent . 37 

Notes of instruction to those in search of the precious metals. 180 
Nickle . 192 

0 

Odor of minerals,. 222 

Oxidizing power of nitrate of potash. 82 

Oxalic acid. Solvent. 31 

Oxygen, Oxidizing reagent. 36 

Osmium . I 95 

P 

Parting of the bead. 101 

Platinic chloride, Precipitant. 34 

Platinum, Assay of. 166 

Potassium bisulphate. Solvent. 30 

bichromate. Oxidizing reagent. 37 

chlorate, Oxidizing reagent. 37 

cyanide, Reducer . 31 

cyanide. Solvent . 31 

hydrate. Solvent . 30 

permanganate, Oxidizer . 37 

permanganate. Oxidizing reagent. 37 

Precipitants . 32 

Preliminary assay. 86 

of a gold bar. 46 

Preliminary examination of ores. 200 

Preparation of the ore sample. 74 

of pure silver. 173 

of pure gold. 173 

Palladium. 195 

Platinum. 191 

R 

Reagents . 26 

Reference table . 19 

Refining of impure copper button. 115 

Resume of operations. 148 

Rich oxidized ores. 114 

Rich sulphurets of copper without lead, lime, or baryta. 114 

Rubidium. 494 






































20(1 


INDEX 


S 

. Page. 

Salt, Flux . 28 

Scale of color. 225 

Scale of hardness. 223 

Scorification. 95 

Selenium, Test for. 206 

Silver amalgam . 242 

Silver ore. Test. 204 

nitrate. Precipitant . 33 

Sodium acetate. Precipitant. 34 

carbonate. Precipitant. 34 

chloride. Precipitant . 34 

chloride. Reducing reagent. 36 

hydrate. Solvent . 30 

hyposulphite. Solvent . 31 

nitrate oxidizer . 37 

Sulphide, Precipitant. 34 

Sulphide, Reducing reagent. 36 

Solvents . 30 

Specific gravity of minerals. 224 

Sulphates, Test . 202 

Sulphur, Blowpipe analysis. 232 

Determination of. 161 

Flux . 113 

Preliminary examination of. 202 

Sulphuric acid. Precipitant. 34 

Solvent . 31 

Sulphurets in quartz. Estimation of. 241 

Sulphuretted hydrogen. Precipitant. 32 

Stannous chloride, Reducing reagent. 36 

T 

Tables, A. T. 246 

Tables of Grain Weights. 248 

Tables, 20 Grammes . 245 

Table for decinormal silver solution. 68 

Table for decinormal salt solution. 67 

Tartaric acid. Solvent. 31 

Taste of minerals. 222 

Tellurides in gold ore. 201 

Tellurium, Preliminary examination of. 201 

Tin Ore, Test. 201 









































INDEX 


267 


Page. 

Tin, Oxide of, Blowpipe analysis. 229 

Table for weir measurement. 250 

Tantallum . 195 

Tellurium. 195 

Thorium . 195 

Thallium. 196 

U 

Universal flux . 80 

Useful Data . 242 

V 

Volumetric determination of iron by potassium permangan¬ 
ate . 125 

Volumetric methods. 115 

Vanadium. 196 

W 

Water measurement. Table for. 250 

Water Solvent . 30 

Weighing. 25 

the charge . 79 

the bead . 99 

gold and silver bead. 99 

Working test for gold and silver ores. 236 

Y 

Yettrium. 196 

Z 

Zirconium . 196 

Zinc, Determination of. 135 

Test . 202 

























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